Crisp puff pastry topped with caramelized onions, Gruyère and thyme—an elegant, savory tart for starters or light meal.
# What You'll Need:
→ For the tart
01 - 1 sheet puff pastry (about 9 oz), thawed if frozen
02 - 3 large yellow onions, thinly sliced
03 - 2 tablespoons unsalted butter
04 - 1 tablespoon olive oil
05 - 1 teaspoon granulated sugar
06 - 1/2 teaspoon fine salt
07 - 1/4 teaspoon freshly ground black pepper
08 - 1 teaspoon fresh thyme leaves
09 - 1 cup grated Gruyère (approximately 4.2 oz)
10 - 1 large egg, beaten (for egg wash)
→ Garnish (optional)
11 - Extra fresh thyme sprigs
12 - Freshly ground black pepper
# How to Make It:
01 - Preheat the oven to 400°F. Line a baking sheet with parchment paper and set aside.
02 - In a large skillet over medium heat, melt the butter with the olive oil. Add the sliced onions, sugar, salt and pepper. Cook, stirring frequently, for 20–25 minutes until deeply golden and caramelized, adding the thyme leaves during the final 5 minutes. Remove from the heat and allow to cool slightly.
03 - On a lightly floured surface, roll the puff pastry to a rectangle about 10 x 14 inches. Transfer the pastry to the prepared baking sheet.
04 - Using a sharp knife, score a 1/2-inch border around the edge of the pastry without cutting through. Prick the inner rectangle all over with a fork to prevent excessive rising.
05 - Brush the scored border lightly with the beaten egg to promote a glossy, golden edge.
06 - Spread the caramelized onions evenly within the scored border and sprinkle the grated Gruyère over the onions.
07 - Bake in the preheated oven for 18–22 minutes, or until the pastry has puffed and turned a deep golden brown and the cheese is melted.
08 - Remove from the oven and let rest for 5 minutes. Garnish with extra thyme and a crack of black pepper. Slice and serve warm or at room temperature.
