Peach and Plum Crostada is the perfect blend of a pie and a crumble, and the addition of plums makes the Crostada even sweeter.
In a bowl, toss fruit with 1 Tbsp. sugar. Let stand for 20 minutes. Preheat oven to 450°F; set rack in lower-middle position. Line a rimmed baking sheet with parchment.
Make topping: In a bowl, rub together 1/4 cup sugar and lemon zest. Stir in flour and salt. Rub in butter using fingertips until mixture is crumbly. Toss in pecans.
On a well-floured surface, roll out puff pastry to a rough 14-inch round. Carefully transfer to baking sheet. Strain fruit mixture (discard juice) and spoon evenly onto pastry, leaving a 2-inch border. Sprinkle topping over filling and fold over edges of pastry. Whisk egg with 1/4 tsp. cold water and lightly brush edges of pastry with egg wash. Refrigerate for 20 minutes.
Bake until pastry has begun to brown, about 20 minutes. Lower heat to 400°F; bake until crust is deep golden brown, bottom is cooked through and filling is bubbling, about 20 minutes longer. Cover with foil if crust is browning too quickly.
Let crostada rest on baking sheet on a wire rack for 10 minutes, then transfer to rack to cool completely. Cut into wedges and serve at room temperature.