Raspberry Poppy Seed Cookies

1 cup confectioners' sugar
1 cup unsalted butter, softened
1 teaspoon vanilla extract
1 egg
2 cups all-purpose flour
3 tablespoons poppy seeds
1/2 teaspoon salt
1/2 cup raspberry preserves, or other flavor

Preheat oven to temperature 300 degrees F.

Beat confectioners' sugar and butter with an electric mixer until light and fluffy. Add vanilla extract and egg. Blend well. Stir in flour, poppy seeds and salt until thoroughly combined. Drop dough by rounded teaspoonsful 1 inch apart on ungreased cookie sheets. Make an indentation in center of each cookie. Fill each with about 1/2 teaspoon of preserves. Bake 20-25 minutes, until golden brown. Remove immediately from cookie sheets.