- 4 medium onions (about 2 lbs. total), thinly sliced lengthwise
- 1 1/2 tablespoons olive oil
- 1 tablespoon chopped fresh thyme leaves, plus whole leaves for garnish
- 1/2 teaspoon kosher salt
- 1/2 teaspoon pepper
- 1 sheet good-quality frozen puff pastry*, such as Dufour (one 14-oz. pkg.), thawed
- 12 ounces jarred roasted red peppers, drained and cut into strips
- About 1/2 cup pitted Niçoise olives
- 2 tablespoons drained capers
- 4 ounces good-quality canned tuna packed in olive oil
- calories 261
- caloriesfromfat 52 %
- protein 7 g
- fat 15 g
- satfat 3.4 g
- carbohydrate 24 g
- fiber 2.5 g
- sodium 541 mg
- cholesterol 3.1 mg
How to Make It
Cook onions in oil in a large nonstick frying pan over medium heat, stirring often, until soft, 8 to 10 minutes. Reduce heat to low and cook, stirring occasionally, until onions are very limp and deep golden brown, about 45 minutes longer. Stir in chopped thyme, salt, and pepper and let cool.
Preheat oven to 400°. Cover a large baking sheet with parchment paper and spread puff pastry over it. Bake until puffed and golden brown, 18 to 20 minutes.
Spread onion mixture over pastry, leaving a thin border (toppings will deflate pastry).
Arrange roasted red peppers in a grid of squares over onions, add 2 olives to each square, and sprinkle with capers. Bake until pastry is well browned, 10 to 15 minutes longer. Sprinkle with whole thyme leaves. Flake a little tuna onto each square.
Slide tart onto a board and cut into squares. Serve warm or at room temperature.
*Puff-pastry packages vary. Pepperidge Farm's 3-oz. package contains 2 sheets; if using, spread the sheets on separate baking sheets and bake 12 to 15 minutes, then divide toppings between the two and bake 10 to 12 minutes longer.