Grease a 13 x 9 x 2 inch baking pan; set aside. In a large mixing bowl beat cream cheese and butter (or margarine) with an electric mixer on medium to high speed for about 30 seconds or until combined.Add about half of the flour to the cream cheese mixture. Then add the sugar, eggs, milk, baking powder, baking soda, and vanilla. Beat on low speed until thoroughly combined, scraping the side of the bowl. Beat on medium speed for 2 minutes. Then beat in remaining flour on low speed just until combined.Spread batter evenly in the prepared pan. Dollop preserves in small spoonfuls on top of the batter. Using a small narrow spatula or knife, gently swirl preserves into the batter to create a marbled effect.Bake in a 350F oven for 30 to 35 minutes or until a wooden toothpick inserted near the center comes out clean. Cool in pan on a wire rack for 15 minutes. Sift powdered sugar over the top. Cut into squares and serve warm or cooled.