Caramelized Onion Tart ♥ (Swiss Onion Cheese Flan)

Caramelized Onion Tart, another creative vegetarian idea for Thanksgiving ♥ Time-Adaptable (Cooking and Serving). Make-Ahead Friendly. Weeknight Easy, Weekend Special. Includes recipe, insider tips, nutrition and Weight Watchers points.
A simple but sophisticated tart, rich enough to serve in thin slices as an appetizer or in larger wedges for a vegetarian main dish. The crust is super un-fussy and flecked with cornmeal for crispness. The filling is packed with caramelized onions, those dark and dusky nuggets that make almost anything taste better. Both the crust and the filling can be made ahead of time, then tossed into the oven to bake in time for serving hot, warm or at room temperature.

Vegetarian Entrée or Appetizer, Perfect for Thanksgiving. Time-Adaptable (Cooking and Serving). Make-Ahead Friendly. Weeknight Easy, Weekend Special.

To The Lovely Someone Who Introduced Me to Gourmet Magazine: Thank You

In some guest room in some home in some city in some country is a basket of paper gold, that is, a basketful of vintage issues of the now-defunct and already much-missed Gourmet magazine. I only wish I could remember whose home! I do remember being unable to sleep on multiple visits, so taken with the classic recipes of another time, madly copying especially enticing ones onto 3x5 cards.

The Caramelized Onion Tart was called "Swiss Onion Cheese Flan" in the December 1967 issue of Gourmet and no where, no where, is is to be found on the Internet. I kind of like that, don't you? Vive le Papier!

It's quite lovely, this tart, with onions cooked to that golden-brown stage where they're silky and caramel-like. The crust too is especially easy, just a fork-stirred dough of cream, milk and flour, rolled in cornmeal for a crisp bite on the outside, almost yeasty inside. Delectable – and a good option for the pastry-impaired.

Let's Talk About This Crust

First off, I've fixed the issue that caused readers trouble. The recipe was originally published with 2 cups of flour and 1 cup liquid, a ratio which created a sticky mess. The recipe has been re-tested and re-written with just 3/4 cup liquid, that works beautifully. Again, I am so sorry, I suspect a typo got the best of me. :-(

The good news is, this just might be the easiest homemade crust I've ever made, just three ingredients, flour, salt and milk/cream. And it's super-tender and I just love rolling the crust dough in cornmeal for a savory tart.

But. This is also a tart crust. By design, it's sturdier than a pie crust because it needs to hold up to the weight of the tart. A traditional flaky, tender pie crust will work here too but it just can't/won't be as strong: you couldn't hold it out in your hand, say. That wouldn't stop me from using a traditional crust, but it's good to know.

If you choose a traditional pie crust, allow me to recommend my own half-butter and half-shortening/lard crust, Flaky Tender Pie Crust, you'll savor every single bite! It comes with step-by-step photo instructions that bakers rave about, How to Make Flaky Tender Pie Crust.

The Filling: Luscious Caramelized Onions

Caramelized onions are kinda dreamy, right? The recipe below includes instructions for making just enough onions for the tart on the stovetop but if you already have lots of caramelized onions on hand, this tart is a great way to use them, also a good way to cook the onions even days ahead for a big meal like Thanksgiving.

Here's how I make Caramelized Onions, Slow Cooker Caramelized Onions either in an actual slow cooker or slow-cooked in the oven. For this tart, you'll want three cups of caramelized onions.


"... the filling ... was really delicious and got lots of wonderful comments, including a promise to make this for next year's gathering." ~ Judie
"The filling was really good ..." ~ Anonymous

Happy Thanksgiving, all! See you after the holiday!

Just updated. First published way back in 2009!


Hands-on time: 50 minutes
Time to table: 75 minutes
Serves 8 in entrée-size wedges, 16 in slim appetizer servings

2 cups flour, fluffed to aerate before measuring or 250 grams
3/4 cup half & half (or 6 tablespoons whole milk plus 6 tablespoons heavy cream)
1 teaspoon table salt
Baking spray & plastic wrap

2 tablespoons butter
3 medium brown-skinned yellow onions (which brown better), chopped to yield about 3 cups
Kosher salt to taste

2 large eggs
1 cup half & half (or 1/2 cup whole milk plus 1/2 cup cream)
4 ounces Parmesan (or another pungent aged slightly dry cheese), grated or even just roughly chopped
1 teaspoon fresh thyme leaves, optional

Fine-grained yellow cornmeal, for rolling the crust

MIX THE CRUST In a medium bowl, use a large fork to lightly toss the flour and salt in until it's light and completely mixed. Spread the flour mixture evenly across the bowl, then drizzle the half & half onto the flour, directly wetting as much flour as possible. Use the fork to toss the flour and half & half until all the flour is moist. If needed, add more milk but do it very judiciously, only a half teaspoon at a time, wetting any still-dry areas. Spray a length of plastic wrap (that's big enough to enclose a disk of dough) and spray with baking spray. With your hands pull the dough together and form a flat disk about six inches wide, place on the plastic wrap and wrap the wrap (haha) around the disk. Refrigerate for at least 30 minutes, as much as a few hours.

COOK THE CARAMELIZED ONIONS In a large skillet, melt the butter on medium heat until shimmery. Add the onions and salt and stir to coat with fat. Cook, stirring often, until the onions turn golden and then brown, adjusting the heat to avoid burning the onion. Let cool.

MAKE THE TART Set the oven to 425F/220C.

To roll out the crust, sprinkle a clean counter with cornmeal, with your hands, cover the outside of the dough with a light layer of cornmeal. Roll out the crust to be the size of the baking dish plus about an inch. Arrange in the baking dish, then the extra dough hanging over the side to the inside and pinch to form an attractive edge.

To miX the filling, in a bowl, whisk the eggs, then whisk in the half & half, Parmesan and thyme. Turn in the cooled onions, then turn the mixture into the prepared crust.

Bake for 15 minutes at 425/220C.

Reduce the heat to 325F/160C, bake for about 25 minutes or until the center is mostly set (a very slight jiggle is okay, it will continue to cook outside the oven) and the crust is golden and crusty.

Let cool slightly, then serve hot or if you like, wait a bit and serve at room temperature.

SLOW COOKER CARAMELIZED ONIONS If you have caramelized onions on hand, use about 3 cups instead of cooking onions especially for the tart, I use these Slow Cooker Caramelized Onions. Just be sure to drain before adding to the tart filling.
BROWNING THE BOTTOM CRUST This is an issue that all pie and tart bakers, including me, struggle with. Here's what I do. (1) First, roll the crust quite thin. Many recipes are written to accommodate varying pan sizes and skill levels; there's usually way too much dough. I often slice off up to a third of the rolled dough. (2) Second, place a baking stone in the bottom rack, this helps radiate heat from the bottom up. Lacking a baking stone, put a baking sheet upside down on the rack where you'll bake the tart, you might needs to drop the rack to a lower slot to keep the tart itself in the center. Either way, pre-heat the baking stone or baking sheet while the oven comes to temperature. (3) Give the oven extra time to not only reach but stay at temperature, a good extra 15 or 20 minutes. (4) Bake in a very hot oven (here, 425F) at first, then finish baking at a lower temperature (here 325F). Good luck, this is always a challenge!

THE DAY BEFORE Make the dough and refrigerate. Cook the onions and refrigerate.
DAY OF Roll out the dough and, if need be, refrigerate. Mix the egg mixture and refrigerate. Just before baking, heat the oven, combine the onion and egg mixtures and turn into the pie crust. Bake and serve.

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from Kitchen Parade, my food column

SEASONAL EATING: Last-Minute Thanksgiving Ideas ACROSS THE YEARS

Secret-Ingredient Cookies with Pecans Green Beans with Lemon & Pine Nuts Curried Cauliflower Veggies for Kids: One Very Sneaky Mom Marinated Vegetable Salad Weight Watchers Pumpkin Smoothie & Weight Watchers Mocha Smoothie How Not to Buy Acorn Squash (Essay) Surprise Weight Watchers Truffles Green Beans with Browned Butter & Pine Nuts Celery Salad with Dates & Walnuts Quick Green Chile Stew (< make this before starting to cook Thanksgiving dinner!) Caramelized Onion Tart Simple Scalloped Potatoes How to Cook Dried Chickpeas Especially for Hummus aka "Jerusalem Chickpeas" (< a game-changer for hummus from scratch!) Roasted Eggplant “Hummus" (Eggplant & Chickpea Dip & Spread) No-Bake Pumpkin Cream Pie

Looking for healthy new ways to cook vegetables? A Veggie Venture is home to hundreds of super-organized quick, easy and healthful vegetable recipes and the famous asparagus-to-zucchini Alphabet of Vegetables. Join "veggie evangelist" Alanna Kellogg to explore the exciting world of common and not-so-common vegetables, seasonal to staples, savory to sweet, salads to sides, soups to supper, simple to special.

© Copyright Kitchen Parade 2009 & 2019

Alanna Kellogg
Alanna Kellogg

A Veggie Venture is home of "veggie evangelist" Alanna Kellogg and the famous asparagus-to-zucchini Alphabet of Vegetables.


  1. With vegetarian kids in our family, I'm always looking for substantial dishes that can be the centerpiece of a meatless holiday meal. This one will definitely be on our table during this holiday season.

  2. This sounds delicious and exactly what I'm looking for to take to a Thanksgiving party. One quick question - what kind of cream - 1/2 & 1/2, heavy?

  3. Judy ~ you could use half & half to substitute for both the cream and the milk, otherwise use heavy cream. Hope you enjoy it! BTW I used it for an appetizer for a party on Saturday, it had been out of the oven for a couple of hours and I just served at room temperature.

  4. I made the tart for a neighborhood Thanksgiving gathering. Well, I made the filling, which was really delicious and got lots of wonderful comments, including a "promise to make this for next year's gathering." I tried to make the crust and had nothing but a sticky mess - I used all 1/2 and 1/2 as you suggested (1 cup) and followed the rest of the crust recipe exactly. Fortunately I had a refrigerated pie crust available to use, so the tart came out wonderfully and no one knew the difference. I'm disappointed the crust didn't turn out tho - I'd much rather not use a refrigerated crust. Any thoughts? Thanks for the recipe!

  5. Judie ~ I'm so glad you had that extra crust hanging around, also that you got such good reviews for taste! But hmm, I just can't think what might have happened with the crust. I found it most easy to work with, not in the least bit sticky. Did you measure the flour by volume or by weight? I'm trying to give both pieces of information now but maybe you measured by volume and used less than the volume by weight? It's the only thing that comes to mind.

  6. I did measure by volume, using a scoop to get the flour into the measuring cup and then sweeping off the excess. Maybe the dip and sweep method would have worked better - or better yet, maybe I should invest in a scale and not have that problem again.

  7. This looks so good, I can't wait to try it out. Thank you for sharing and for making me hungry -

  8. I definitely recommend a kitchen scale and can't wait to make this as a side for Thanksgiving this year.

  9. I tried this recipe last night. The filling was really good - but the crust was left behind by almost everyone. Next time, I will experiment with the flavors in the filling and make the most excellent Joy of Cooking pie crust. Perhaps some sage instead of thyme. Thanks for the recipe!

  10. Anonymous ~ Well heck, that's two of you who've had trouble with the crust. It's been two years now since I've made this but my notes from the time, "... crisp bite on the outside, almost yeasty inside. Delectable - and a good option for the pastry-impaired" match my memory that it was a great almost yeasty crust that was easy to handle. To you both, so sorry, my experience was obviously different. It may work its way onto a menu in the next few weeks ... I'll let you know how it goes.


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Thank you for taking a moment to write! I read each and every comment, for each and every recipe, whether a current recipe or a long-ago favorite. If you have a specific question, it's nearly always answered quick-quick. ~ Alanna