Mix butter, cream cheese, vanilla and sugar in a bowl, and beat with mixer until fluffy. Stir in flour and salt until a soft dough is formed. Cover and refrigerate 2-3 hours.
Preheat oven to 350. Spray cookie sheets with cooking spray, set aside. Roll dough to 1/8" thickness on lightly floured board.
With a cookie cutter, or glass (I use a glass jar), cut dough into 3" rounds. Place 1/4 tsp. jam in center, fold in half and crimp edges with a fork. Pierce top of each cookie with a sharp knife for steam release. Arrange cookies on greased sheet.
Bake 10-12 minutes, until cookies are lightly browned. Cool on wire rack.