1 3/4 cups all-purpose flour
1/2 teaspoon baking powder
1/2 teaspoon fine salt
3/4 cup unsalted butter (1 1/2 sticks), softened
2/3 cup sugar, plus more for rolling
1 large egg
1/3 cup raspberry, cherry or strawberry jam
Preheat oven to 350 degrees F.
Whip the butter and the sugar with a hand-held mixer until fluffy, about 5 minutes. Beat in the egg until just combined.
Slowly beat in the flour, salt & baking powder, mixing just until incorporated.
Scoop the dough into 3/4 -inch balls with a cookie or ice cream scoop and roll in sugar. Place about 2-inches apart on the prepared baking sheets. Press a thumbprint into the center of each ball. Fill each indentation with about 1/4 - 1/2 teaspoon jam.
Bake cookies until the edges are golden, about 15 minutes. (For even color, rotate the pans from top to bottom about halfway through baking.) Cool cookies on baking rack. Serve.