> 3 cups all-purpose flour
> 1 tsp baking powder
> 1/4 tsp salt
> 1 cup (2 sticks) butter, softened
> 1 cup sugar
> 1 large egg
> 2 tsp vanilla extract
> 1/3 cup strawberry or apricot jam
Preheat oven to 350°F. Line 2 large cookie sheets with parchment. In a medium bowl, whisk together the flour, baking powder, and salt.
In a large bowl, using a hand mixer or stand mixer, cream the butter and sugar 2–3 min., until fluffy. Add the egg and vanilla. Mix well. In batches, slowly add dry ingredients on low speed until combined.
Shape dough into 1-inch balls. Arrange on cookie sheets, spacing 1 inch apart. Press a thumbprint in the middle of each cookie and fill with the jam. Bake cookies 8–10 min., until golden, switching racks halfway through. Let cool slightly and transfer cookies to a wire rack to fully cool.