We replaced anchovies with tuna and added roasted red peppers and capers in Tuna and Roasted Red Pepper Pissaladière--our variation to this classic French tart.
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
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.