Prepare to bake. Preheat the oven to 400ºF. Line a baking sheet with parchment paper.
Coat the berries. Combine the berries and sugar in a mixing bowl; lightly stir, then let stand for 5 minutes.
Prepare the crust. Place the puff pastry dough on the previously prepared baking sheet and cut it in half.
Assemble. Spread 2 tablespoons of strawberry jam right down the middle of each pastry sheet. Evenly divide the berries and arrange them over the strawberry jam, down the middle of each pastry sheet.
Bake. Bake for 18 to 20 minutes, or until golden brown.
Rest, then serve. Remove and let the tart stand for a few minutes. Dust with powdered sugar, cut and serve.
Notes
If one side puffs up more than the other during baking, prick the puff pastry with a fork or knife to deflate.