- 1 cup all-purpose flour
- 1 teaspoon sugar
- 1/2 teaspoon salt
- 2 tablespoons unsalted butter, chilled and cut into small pieces
- 2 tablespoons vegetable shortening, chilled
- 3 1/2 - 4 tablespoons cold water
- 1 tablespoon olive oil
- 1 medium Vidalia or other sweet onion, chopped
- 1 teaspoon fresh thyme, chopped
- 1/4 teaspoon salt
- 1/4 cup sugar
- 4 teaspoons sherry vinegar
- 4 1/2 cups assorted color cherry tomatoes
- 1/2 cup mayonnaise
- 2 oil packed anchovy fillets, drained, mashed into a paste
- 1/2 teaspoon grated fresh lemon zest
- For the crust, combine the flour, sugar and salt in a medium bowl. With a pastry blender or 2 forks, cut the butter and shortening into the flour until the mixture resembles coarse crumbs. Stir in the water 1 tablespoon at a time until a dough begins to form. Knead the dough several times to bring it together. Shape into a 4-inch disk, wrap in plastic wrap and refrigerate until ready to use.
- Preheat the oven to 425°F.
- For the filling, heat the oil in a 12-inch nonstick skillet over medium. Add the onion, thyme and salt; cook, stirring occasionally, until onions are softened and slightly browned, about 10-11 minutes. Transfer the onions to a bowl.
- Return the skillet to the stove over medium heat and add the sugar, 1/4 cup water, and vinegar. Swirl the pan until the sugar dissolves. Bring the mixture to a boil and cook until golden, about 5-6 minutes. Remove the skillet from the heat and stir in the onion mixture and tomatoes until well combined.
- On a lightly floured surface, roll out the crust into a 12-inch circle. Place the crust over the tomato mixture, tucking the edges of the dough between the tomatoes and the side of the skillet. Prick the dough several times with the tines of a fork or the tip of a knife.
- Bake the tart until the crust is nicely browned, 30 minutes. Remove from the oven and let stand 5 minutes. Place a rimmed serving platter that is larger than the skillet over the top of the pan. Carefully and quickly flip the skillet and platter over to allow the tart and any liquid in the pan to fall onto the platter. Let cool 10 minutes before cutting into wedges.
- Meanwhile, combine the mayonnaise, mashed anchovies and lemon zest in a small bowl. Serve each tart wedge with a dollop of the mayonnaise.