Description
This Caramelized Onion Tart is a golden, flaky puff pastry topped with deeply caramelized onions and rich Montasio cheese. Elegant yet simple, it’s perfect for dinner parties, holidays, or cozy nights in—an impressive vegetarian dish bursting with flavor and texture.
Ingredients
- 1 sheet frozen puff pastry, thawed (about 8 oz / 225 g)
- 2 tablespoons olive oil
- 2 tablespoons unsalted butter
- 2 large sweet onions, thinly sliced (about 1.5 lbs / 680 g)
- 1/4 teaspoon kosher salt
- 1/2 teaspoon dried thyme (or 1 teaspoon fresh thyme)
- 1 teaspoon sugar
- 2 teaspoons balsamic vinegar
- 2 oz (56 g) grated Montasio cheese (or Fontina or Gruyère)
- 1 egg, lightly beaten (for egg wash)
Instructions
- Preheat oven to 400°F (200°C).
- On a floured surface, roll puff pastry to fit tart pan or form a rustic rectangle. Fold edges slightly for a border.
- Heat olive oil and butter in a skillet over medium heat.
- Add sliced onions and salt. Cook 25–30 minutes, stirring often, until golden and soft.
- Stir in thyme, sugar, and balsamic vinegar; cook 2–3 minutes more.
- Spread caramelized onions evenly over pastry.
- Sprinkle grated cheese on top.
- Brush edges with beaten egg for a golden crust.
- Bake 20–25 minutes until pastry is puffed, golden, and cheese is melted.
- Cool a few minutes before slicing.
Notes
- Thaw puff pastry in the fridge for best results.
- Caramelize onions slowly over low heat for deep flavor.
- Keep onion mixture dry or pre-bake pastry for 5 minutes to prevent a soggy crust.
- Caramelize onions up to 2 days in advance; assemble and bake when ready to serve.
- Refrigerate up to 3 days or freeze up to 1 month. Reheat at 350°F (175°C) for 10 minutes.
- Prep Time: 15 minutes
- Cook Time: 30 minutes
- Category: Appetizer
- Method: Baked
- Cuisine: French
Nutrition
- Serving Size: 1 slice
- Calories: 290
- Sugar: 6g
- Sodium: 260mg
- Fat: 20g
- Saturated Fat: 9g
- Unsaturated Fat: 10g
- Trans Fat: 0g
- Carbohydrates: 22g
- Fiber: 2g
- Protein: 6g
- Cholesterol: 45mg
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