Cookies
1 cup butter or margarine, softened
1/3 cup powdered sugar
1 teaspoon vanilla
1 2/3 cups Gold Medal® all-purpose flour
1 tablespoon powdered sugar
Filling
2/3 cup granulated sugar
2 to 3 teaspoons grated lemon peel
3 tablespoons lemon juice
1 tablespoon butter or margarine
1 teaspoon cornstarch
1/4 teaspoon salt
1 egg, beaten

1. In large bowl, beat butter, 1/3 cup powdered sugar and the vanilla with electric mixer on medium speed until well blended. Stir in flour until dough forms. Cover; refrigerate 30 minutes for easier handling.
2. Heat oven to 350°F. Shape dough into 1-inch balls. On ungreased cookie sheets, place balls 2 inches apart. Press thumb into center of each ball to make indentation.
3. Bake 8 to 10 minutes or until light golden brown. Immediately remove from cookie sheets to cooling racks. Cool completely, about 30 minutes.
4. In 1-quart saucepan, heat all filling ingredients over low heat about 25 minutes, stirring constantly, until smooth and thickened. Cool slightly, about 15 minutes.
5. Fill each thumbprint with rounded 1/4 measuring teaspoon filling. Sprinkle 1 tablespoon powdered sugar over cookies.

Source: bettycrocker.com