1. Heat oven to 375 degrees F. Sift together first four ingredients.
2. In a large bowl, beat together butter, 2/3 cup sugar, egg and vanilla; gradually beat in flour mixture.
3. Shape dough into 32 balls; roll in 1 1/2 tablespoons sugar and arrange 1 1/2 inches apart on a parchment-paper-lined baking sheet.
4. Press your thumb into the center of each cookie; fill with preserves. Bake 10 minutes.