To prepare the filling, beat the first 5 ingredients at medium speed of a mixer until well-blended, and set aside.
To prepare the brownies, coat the bottom of an 8-inch baking pan with cooking spray (do not coat the sides of the pan). Lightly spoon 3/4 cup flour into dry measuring cups, and level with a knife. Combine the flour, baking powder, baking soda, and salt in a medium bowl. Combine 1 cup sugar and the next 6 ingredients (1 cup sugar through the 2 egg whites), stirring well with a whisk. Add to the flour mixture, stirring just until moist. Spread two-thirds of batter in bottom of prepared pan. Pour filling over batter, spreading evenly. Carefully drop the remaining batter and preserves by spoonfuls over filling; swirl together using the tip of a knife to marble. Bake at 350° for 40 minutes or until a wooden pick inserted in center comes out almost clean. Cool on a wire rack.