Golden Caramelized Onion & Gruyère Puff Pastry Tart Recipe
This Golden Caramelized Onion & Gruyère Puff Pastry Tart features sweet, jammy caramelized onions combined with nutty Gruyère cheese on a flaky puff pastry crust. Enhanced with fresh thyme and a hint of Dijon mustard, this elegant yet easy-to-make tart is perfect for appetizers, brunch, or a light meal.
- Prep Time: 15 minutes
- Cook Time: 40 minutes
- Total Time: 55 minutes
- Yield: 6 servings 1x
- Category: Appetizer
- Method: Baking
- Cuisine: French
Ingredients
Scale
Pastry and Topping
- 1 sheet puff pastry, thawed (about 10×10 inches)
- 1 egg, beaten (for brushing edges)
- 1 tbsp Dijon mustard (optional, for flavor depth)
- 1 cup (100 g) shredded Gruyère cheese
- ¼ cup (60 ml) heavy cream
- 1 egg
- ½ tsp black pepper
- 1 tsp fresh thyme leaves (plus more for garnish)
- Salt, to taste
- Sea salt, for finishing
Caramelized Onions
- 3 large yellow onions, thinly sliced
- 2 tbsp butter
- 1 tbsp olive oil
- 1 tsp sugar
Instructions
- Prepare the caramelized onions: In a large skillet, melt the butter with olive oil over medium heat. Add the thinly sliced onions, sugar, and a pinch of salt. Cook slowly, stirring often, for 25–30 minutes until the onions become golden brown and jammy. Stir in 1 tsp fresh thyme leaves, then set aside to cool slightly.
- Preheat oven and prepare pastry: Preheat your oven to 400°F (200°C). Place the thawed puff pastry sheet on a parchment-lined baking sheet. Score a 1-inch border around the edges without cutting all the way through. Lightly prick the inner section with a fork to prevent excessive puffing.
- Blind bake the pastry edges: Brush the scored edges of the pastry with the beaten egg to achieve a golden color when baked. Bake in the preheated oven for about 10 minutes or until the edges are lightly golden.
- Prepare the cheese mixture: In a mixing bowl, whisk together the heavy cream, 1 egg, black pepper, and shredded Gruyère until smooth and well combined.
- Assemble the tart: Optionally, spread Dijon mustard evenly over the pre-baked pastry base. Pour the Gruyère cheese mixture evenly within the scored border. Generously top the tart with the caramelized onions.
- Bake the assembled tart: Return the tart to the oven and bake for 15–18 minutes until the pastry is puffed, and the cheese mixture is set and golden brown.
- Garnish and serve: Sprinkle fresh thyme leaves and a touch of sea salt over the hot tart. Slice into squares and serve warm or at room temperature.
Notes
- Make sure to cook the onions low and slow to develop a rich caramelized flavor without burning.
- Allow the caramelized onions to cool slightly before adding to the tart to prevent sogginess.
- Dijon mustard adds depth but can be omitted if preferred.
- Use a sharp Gruyère for best flavor and melting quality.
- Scoring the border without cutting through helps keep the edges puffed and the center flatter to hold the toppings.
- Serve this tart as a stylish appetizer, light lunch, or a side dish alongside salads.
Keywords: caramelized onion tart, gruyère tart, puff pastry tart, French tart, appetizer, savory tart
