Preheat oven to 400°F Whisk flour, sugar, and baking powder in a large bowl. Add butter; using your fingertips, rub in butter until coarse meal forms. Whisk egg and yolk in a bowl; add to flour mixture; stir just to blend.

Line 2 baking sheets with parchment paper. Roll into balls. Place on prepared sheets, spacing 2" apart. Make an indentation in center of each ball; fill each with 1/2 teaspoon jam.

Bake cookies until golden, 11–13 minutes. Transfer to a wire rack to cool.