Tarte á l’Oignon — Savory French Onion Tart

A delicious, simple and impressive Alsatian dish to serve next time the next time you host a gathering.

Prep your dough and get to tarting – this savory tart is a French Alsatian delight from my mother in law, Brigitte Helzer. There is also a vegetarian option as you can always cut ham from the recipe. Music: “Cabin by the Sea” by The Diskettes

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Tarte á l’Oignon (Savory French Onion Tart)


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  • Author: Cooking by Heart
  • Total Time: 55 minutes
  • Yield: 4-8 servings 1x

Description

Delicious, simple and impressive dish to serve next time you host!


Ingredients

Units Scale
  • 4-5 large onions, roughly chopped
  • 1-2 tbs. unsalted butter
  • salt, pepper
  • 1/2 tsp. nutmeg
  • 2 slices ham or prociutto, roughly chopped
  • 1 tbs. all-purpose flour
  • 1 egg
  • 1/2 cup (120 ml) milk
  • 1 cup (240 ml) emmentaler, grated (could sub in some gruyere or swiss or other cheeses)

Instructions

  1. Have savory dough ready – I like to have it rolled out on my pan then I keep it cold in the fridge til I’m ready. I have an awesome flaky savory dough recipe in my Tarte á la Tomate post.
  2. Preheat oven to 450
  3. Heat butter over low-medium flame
  4. Add onions, stir and cover to sweat
  5. This is a good time to grate cheese, roughly chop ham or prociutto
  6. Add ham or prociutto to sweated onions
  7. Add flour
  8. In a separate bowl, whisk egg and milk together
  9. Turn off flame, add mixture to onions
  10. Pull out your prepped dough, pour in onions
  11. Generously sprinkle grated cheese on top
  12. Bake at 450 for 20 mins, then reduce heat to 350 for another 20 mins, cheese and edges of crust should be golden brown
  13. Let cool for 10 mins on cooling rack before digging in
  14. Enjoy!
  • Prep Time: 15 minutes
  • Cook Time: 40 minutes
  • Category: Side Dish
  • Cuisine: French Alsatian

Nutrition

  • Serving Size: 1 slice
  • Calories: 290

 

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Frequently Asked Questions

Can I make this tart vegetarian?

Yes — the article explicitly states: “there is also a vegetarian option as you can always cut ham from the recipe.” Simply omit the 2 slices of ham or prosciutto; the caramelized onion, egg, milk, and cheese filling is hearty enough on its own.

What cheese works best, and can I substitute?

The recipe calls for 1 cup of grated emmentaler, the traditional Alsatian choice. The ingredients list itself says you “could sub in some gruyere or swiss or other cheeses” — any good melting cheese with mild nuttiness will work well.

Why does the oven temperature drop partway through baking?

The tart starts at 450°F for 20 minutes to set the crust and start browning the cheese, then the temperature drops to 350°F for another 20 minutes so the egg-and-milk custard cooks through gently without burning the top. The cheese and edges of the crust should be golden brown when done.

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