This old-fashioned thumbprint cookies recipe is inspired by one my grandmother used to always make. The raspberry thumbprint cookies are buttery, rich, crumbly, and delicately sweet (similar to the flavor and texture of shortbread), with most of the sweetness coming from the jam. The buttery, slightly salty flavor is full of nostalgia for me, but if you prefer your cookies sweeter, you can sift a little confectioners’ sugar over the top of the finished classic thumbprint cookies.