Whip together cream cheese and butter. Add flour. Roll dough into long log; wrap in waxed paper. Chill until firm. Slice into 1/4-inch slices. Put thumbprints in middle of each slice after slices are put on cookie sheet. Put 1/2-teaspoon jam into thumbprint of each slice. Bake until golden in 350° oven 10 minutes. Cool. Sprinkle with sifted powdered sugar.