French Onion Tart Recipe

This delicious Provençal French Onion Tart has a 2-ingredient filling of braised onions and eggs, baked in a mustard-coated pie shell. It can be a very quick easy recipe if you start with a pre-made pie crust, and it makes a fantastic main dish for brunch or for a Mediterranean-inspired dinner. 

The first time I made this French onion tart, I was amazed by its rich deliciousness and depth of flavor. I wondered how something so simple could be so tasty. There's no cheese here, just lots of braised onions, a couple of eggs, a little olive oil and salt. It's a testament to Provence, known for its simple, healthy, scrumptious cuisine.

How To Make This French Onion Tart

The only time-consuming part of this recipe is making the homemade pie crust. For a quick and easy version, start with a pre-made crust.

1. Make the tart shell or start with a purchased, pre-made pie crust. 
2. Pre-bake the crust, let it cool, and brush the insides with Dijon mustard.
3. Braise 4 large sliced onions in a large heavy pot, with a little oil, water and salt, to soften them and coax out their natural sugars.
4. Mix the braised onions with 2 eggs, and load them into the mustard-coated tart shell.
5. Arrange thyme sprigs and Niçoise olives on top to give the tart a lovely French country look, and bake for 30-40 minutes, until golden brown.
6. Serve at room temperature.

Crying over onions is a good thing

This onion tart recipe always gets me crying my eyes out from cutting all those onions. Did you know that If not for tears, the chemicals in onions could damage your eyes?

I learned this fact and a lot about the topic of tears back when I worked for ABC News 20/20 and produced a segment on crying. I visited a scientist in Minnesota named Dr. William Frey, who was studying the chemical composition of tears. He gave people test tubes to collect their irritant tears and emotional tears so he could study the differences.

First he'd sit them in a screening room and show them a tear-jerker of a scene from an old Jimmy Stewart movie to gather their emotional tears. Then he'd have them lean over a blender full of freshly-pureed onions, to collect their irritant tears. Dr. Frey discovered chemicals in emotional tears that were not present in irritant tears. His research has shown that the reason we feel better after a good emotional cry is, we are literally ridding our bodies of toxins associated with stress.

It's a comfort to know that whether you're crying for emotional reasons or because you're making this French onion tart, your tears are beneficial.

What to serve with this French Onion Tart

I love this tart as much for brunch as for dinner. With a simple green salad on the side, it makes a perfect summer meal. It also works well as a side dish. I recently made it for dinner, for my book group, with grilled Aleppo pepper chicken and ratatouille. The meal was fantastic - healthy and flavorful - and not too hard organize because I made the ratatouille and the tarts ahead of time. 

A big thank you to my friend Diane Rao for this wonderful French onion tart recipe. She gave me a fantastic cookbook called A Passion for My Provence, which is my source for this "Tarte campagnarde a l'oignon." By the way, Diane is an expert on all things French. If you're planning a trip to Paris, you should check out Diane's Instagram for some great ideas and inspiration.

I hope you enjoy this tart. And if you find a way, other than onion goggles, to get through this recipe without crying your eyes out, I would like to know your secret.

Here's the French Onion Tart Recipe. If you try this recipe I hope you'll come back to leave a star rating and a comment. I'd love to know what you think.

French Onion Tart Recipe

Print Recipe

★★★★★

5 from 1 reviews

A savory vegetarian tart of braised onions and eggs baked in a mustard-coated tart shell, topped with thyme and olives. Perfect for brunch or dinner.

• Author: Lisa
• Prep Time: 2 hours
• Cook Time: 1 hour
• Total Time: 3 hours
• Yield: 8 1x
• Category: Side dish
• Method: Bake
• Cuisine: French

Ingredients

Scale 1x2x3x

For The Tart Shell 

• 1 stick cold unsalted butter
• 1 cup unbleached all-purpose flour
• ¼ teaspoon salt
• 3 tablespoons cold water

For The Filling

• 3 tablespoons olive oil
• 4 large onions, thinly sliced (about 6 cups)
• 1 teaspoon salt
• 2 eggs, whisked
• 1 tablespoon dijon mustard

To Garnish

• 5-6 thyme sprigs
• 6-8 Niçoise olives

Instructions

1. Make The Tart Shell Cut butter into small chunks and transfer to the bowl of a food processor fitted with the s-shaped chopping blade. Add flour, and salt. Pulse about 10 times. Then add the water and pulse about 10 more times or until the texture resembles cornmeal. Pour the mixture onto a clean surface and, using the heal of your hand, press it little by little, until the butter and flour are incorporated. Gather it into a ball. Flatten the ball into a disc. Cover with wax paper and refrigerate for 15 minutes, to firm it up a bit. Generously dust your work surface and rolling pin with flour to prevent sticking. Remove the dough from the fridge and roll it into a 13-inch circle. Line a 9 or 10-inch tart pan with the dough, trimming off the excess. Make several pricks in the bottom with a fork and refrigerate for 2 hours. (It can also be frozen until you're ready to use it)
2. Preheat oven to 400ºF. Cover the tart shell with foil and fill the bottom with dried beans. Bake it in the middle of your oven for 10 minutes. Remove the beans and foil and bake for another 5-10 minutes. You want the bottom to dry without coloring.
3. Make The Tart: Preheat the oven to 425ºF. In a large dutch oven or heavy pot combine olive oil, sliced onions, salt and ¼ cup of water. Heat the mixture until it starts to sizzle, then turn the heat down to a simmer, cover, and cook for 30 minutes, stirring occasionally. Spoon onions into a mixing bowl and set aside until cool. Pour off liquid that has accumulated around the onions and combine eggs with onions.
4. Spread mustard over the bottom of the pre-baked tart shell, using a pastry brush. Spread the onion mixture evenly on top. Make a pretty pattern on top with the thyme sprigs and olives. Bake in the middle shelf of the oven for 30-40 minutes, until the top is golden brown. Serve at room temperature, cut into wedges.

Notes

TIME SAVING TIP: To make this recipe quick and easy, use a store-bought pie crust.

Keywords: Onion tart, savory vegetarian tart

Originally published April 7, 2013. Updated April 10, 2021 with clarifying details and step-by-step instructions added to the written post. Same delicious recipe!