French Onion Tart Recipe

French Onion Tart slow-caramelizes yellow onions into jammy sweetness, spreads over mustard-kissed puff pastry, bakes with Gruyere till golden bubbly crisp. French appetizer dazzles in 60 minutes, flaky base holds rich onion cheese layers. Serves 6-8 as elegant starter.

French Onion Tart Recipe

Caramelized onions on puff pastry with Gruyere. Flaky French appetizer, savory sweet.

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Prep Time 20 minutes mins

Cook Time 40 minutes mins

Total Time 1 hour hr

Servings: 8

Course: Appetizer

Cuisine: French

Calories: 320

Ingredients Equipment Method Notes

Ingredients

  

For the Onions

• 4 large yellow onions thinly sliced
• 3 tbsp unsalted butter
• 1 tsp fresh thyme leaves

For the Tart

• 1 sheet puff pastry thawed
• 1½ cups grated Gruyere cheese
• 2 tbsp Dijon mustard
• 1 egg beaten for wash
• ½ tsp salt
• ¼ tsp black pepper

Equipment

• Large skillet
• Rolling Pin
• Baking sheet parchment
• Measuring cups & spoons

Method

 

1. Melt butter in large skillet over medium-low using measuring spoon. Add sliced onions and thyme with wooden spoon. Cook 35-40 minutes stirring often till deep golden soft jammy, no burn.
2. Preheat oven 400°F. Line baking sheet parchment. Roll puff pastry rectangle 12×10 inches using rolling pin on floured board. Transfer sheet. Spread Dijon even with back spoon. Season salt pepper from measuring spoons.
3. Scatter caramelized onions over mustard uniform ½-inch edge border. Sprinkle Gruyere cheese full cover. Brush edges egg wash using pastry brush for golden shine.
4. Bake middle rack 20-25 minutes till pastry puffs deep gold, cheese bubbles brown. Cool rack 10 minutes for clean slice.
5. Cut 8 wedges with pizza cutter or knife. Serve warm or room temp with greens.

Notes

• Yellow onions sweeten perfect; cook low patient for jam texture.
• Thaw puff pastry fridge overnight, don’t overwork or tough.
• Make onions ahead fridge 3 days. Tart freezes baked, reheat 375°F 10 minutes.