Lightly spoon flour into dry measuring cups; level with a knife. Combine flour and salt, stirring well with a whisk; set aside.
Place sugars, peanut butter, and butter in a large bowl; beat with a mixer at medium speed until well combined. Add eggs, 1 at a time, beating well after each addition. Beat in vanilla. Gradually add flour mixture to sugar mixture, beating on low speed just until combined.
Lightly coat hands with cooking spray. Shape dough into 36 balls (about 2 1/2 teaspoons each). Place balls 2 inches apart on baking sheets lined with parchment paper. Press thumb into center of each dough ball, leaving an indentation. Cover and chill 1 hour.
Preheat oven to 350°.
Uncover dough. Bake at 350° for 14 minutes or until lightly browned. Remove cookies from pans, and cool on a wire rack.
Place preserves in a small microwave-safe bowl, and microwave at HIGH 20 seconds, stirring once. Add juice, stirring until smooth. Spoon about 1/2 teaspoon preserves mixture into the center of each cookie.