French-Inspired Caramelized Onion and Gruyère Tart

By AislePrompt Editorial · ·

How this recipe was made — this recipe was drafted by AislePrompt's AI-assisted pipeline from technique templates and USDA-sourced nutrition data, and published by AislePrompt Editorial — see how AislePrompt recipes are drafted and published.

A buttery tart crust filled with sweet caramelized onions and nutty Gruyère cheese, perfect for a comforting appetizer or light meal. This French-inspired recipe, ready in about 55 minutes, layers store-bought puff pastry sheet, thawed, yellow onions, thinly sliced, unsalted butter into a dessert worth slowing down for — great for weekend baking, holiday tables, or any time you want a sweet payoff at the end of a meal. Each serving lands at about 320 calories and feeds 6, so it slots into a weekend bake or a special-occasion dessert tray. Tap "Plan a meal with the AI" below to drop this recipe into your week and send the ingredients straight to Instacart. Nutrition values are approximate, calculated from USDA FoodData Central (fdc.nal.usda.gov) — verify against ingredient labels for any health-driven dietary plan.

Prep: 15 min Cook: 40 min Serves 6 French cuisine 320 cal/serving
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Ingredients

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Instructions

  1. Step 1: Preheat oven to 400°F (200°C). In a large skillet, melt 3 tbsp unsalted butter over medium-low heat. Add 3 thinly sliced yellow onions, 1 tsp salt, and 1/2 tsp black pepper. Cook slowly, stirring occasionally, for 30-35 minutes until the onions are deeply caramelized and golden brown.
  2. Step 2: Roll out 1 sheet thawed puff pastry on a parchment-lined baking sheet. Using a sharp knife, score a 1-inch border around the edges without cutting all the way through.
  3. Step 3: Spread the caramelized onions evenly inside the scored border. Sprinkle 1 cup grated Gruyère cheese over the onions, then scatter 1 tsp fresh thyme leaves on top.
  4. Step 4: Brush the exposed pastry border with 1 beaten large egg to give it a golden finish. Bake the tart for 25-30 minutes until the pastry is puffed and golden and the cheese is melted and bubbly.
  5. Step 5: Let the tart cool for 5 minutes before slicing and serving warm or at room temperature.

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