Can I use yellow onions instead of sweet onions?

Yes, though sweet onions like Vidalia or Walla Walla give a gentler, less pungent flavor. Yellow onions will caramelize well but may have a bolder taste.

How long does a caramelized onion tart last?

Store leftovers in an airtight container in the refrigerator for up to 3 days. Reheat in the oven at 350°F for 10 minutes to restore its crispness.

Can I make the tart ahead of time?

Absolutely. Prepare the onions a day or two before and refrigerate. Assemble and bake the tart on the day you plan to serve it.

What is the best cheese substitute for Gruyère?

Emmental , Jarlsberg , or Swiss cheese are great options that melt well and offer similar nutty, creamy notes.

Can I freeze the onion tart?

Yes, once cooled, wrap the tart tightly and freeze for up to one month. Reheat in the oven until warmed through.

Caramelized Onion Tart

Description

This Caramelized Onion Tart is the perfect Thanksgiving side dish, featuring deeply caramelized sweet onions, flaky puff pastry, and creamy Gruyère cheese. Elegant yet simple, it balances savory richness with a hint of sweetness ideal as a side, appetizer, or light meal.

Ingredients

Scale

3 to 4 large sweet onions (Vidalia, Walla Walla, or Maui)
2 tablespoons olive oil
2 tablespoons butter
1 sheet puff pastry (thawed)
2 large eggs
3/4 cup heavy cream
1 cup grated Gruyère or Emmental cheese
1 teaspoon fresh thyme leaves
Salt and black pepper to taste

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Instructions

Thinly slice onions. Heat olive oil and butter in a skillet over medium-low heat. Add onions and a pinch of salt. Cook for 30–40 minutes, stirring often, until golden and caramelized.
Preheat oven to 375°F (190°C). Roll out puff pastry and fit into a tart pan. Prebake for 10 minutes with pie weights, then cool slightly.
Whisk together eggs, cream, thyme, salt, and pepper. Stir in half of the cheese.
Spread caramelized onions over the prebaked crust. Pour in egg mixture and top with remaining cheese.
Bake for 25–30 minutes until set and golden. Cool slightly before slicing.

Notes

For best results, caramelize onions slowly to bring out their sweetness. Prebake crust to avoid sogginess. The tart can be made a day ahead and reheated before serving.

Prep Time: 25 minutes
Cook Time: 45 minutes
Category: Thanksgiving
Method: Baked
Cuisine: French

Nutrition

Serving Size: 1 slice
Calories: 320
Sugar: 8g
Sodium: 340mg
Fat: 23g
Saturated Fat: 12g
Unsaturated Fat: 9g
Trans Fat: 0g
Carbohydrates: 20g
Fiber: 2g
Protein: 9g
Cholesterol: 110mg