Preheat oven to 375°. In a food processor, whirl together flour, granulated sugar, baking powder, salt, and butter until dough is very crumbly, about 2 minutes. Add yolks and pulse until dough just comes together. Or, you can combine ingredients (dry first, then the yolks) in a large bowl using a pastry blender.
Grease a 10-in. tart pan with a removable rim. Press about three-quarters of dough into bottom of pan (no need to press dough up the sides). Spread jam over dough, leaving a 1/2-in. border around edge. Crumble remaining dough over jam to form topping.
Bake until lightly browned and jam is bubbling, about 40 minutes. Let cool 15 minutes before removing from pan. Dust with powdered sugar, if you like.