Caramelized Onion and Olive Tart

By Stina

Ingredients

• 3 tablespoons unsalted butter
• 2 tablespoons extra virgin olive oil
• 4 large onions, halved lengthwise and sliced lengthwise
• 1 1/2 tablespoons fresh thyme leaves or 2 teaspoons dried thyme
• 1 teaspoon salt
• 1/2 cup pitted black olives, such as kalamata, quartered lengthwise
• 3/4 teaspoon black pepper
• 3 cloves garlic
• 1/4 cup tomato paste
• 1 tablespoon anchovy paste
• 1 large egg
• 2 puff pastry sheets (from a 17.3-ounce package); thawed if frozen
• all-purpose flour for dusting and rolling

Preparation

Step 1

Special equipment: parchment paper; a rolling pin; a pastry brush

Melt butter with olive oil in a 5- to 6-quart wide heavy pot over medium heat. Add onions, thyme, and 1 teaspoon salt. Reduce heat to medium low and cook, stirring occasionally, until onions are softened and deep golden brown, 50 minutes to 1 hour. Cool to warm then stir in olives and 1/2 teaspoon pepper.

While onions are cooking (or cooling), mince and mash garlic with a pinch of salt to a paste with a large heavy knife. Transfer to a small bowl and stir in tomato and anchovy pastes and 1/4 teaspoon pepper.

Preheat oven to 425 F with rack in the middle.

Line a large baking sheet with parchment paper. Whisk together egg with 2 teaspoons warm water in a small bowl and set aside. Working with 1 sheet at a time, unfold pastry and dust work surface and top of pastry lightly with flour and roll into a 15- by 12-inch rectangle. Transfer to a baking sheet. Spoon half of tomato mixture over center and spread in a thin layer over pastry, leaving a 1-inch border around the edge. Spread half of the onions over tomato mixture , then fold in edges over onions, pressing down firmly on sides and corners.

Brush top of border lightly with some egg wash and bake until pastry is puffed and golden brown, about 25 minutes. Assemble another tart with remaining pastry, tomato mixture, and onions.

Cool tarts on a rack 10 minutes before cutting each into 12 squares. Serve warm or at room temperature.

Make ahead: Onion mixture can be made up to 2 days in advance and kept covered and chilled. Tart can be assembled 1 day ahead and kept chilled, loosely covered. Brush with egg wash before baking. Baking time may be slightly longer.