Preheat oven to 350°.
To prepare cake, place granulated sugar, 3 tablespoons butter, and cream cheese in a large bowl; beat with a mixer at medium speed until well blended (about 5 minutes). Add egg and egg white, 1 at a time, beating well after each addition. Beat in vanilla. Lightly spoon flour into dry measuring cups; level with a knife. Combine flour, baking powder, baking soda, and salt, stirring well with a whisk. Add flour mixture and buttermilk alternately to sugar mixture, beginning and ending with flour mixture.
Pour batter into a 9-inch round cake pan coated with cooking spray. Bake at 350° for 30 minutes or until wooden pick inserted in center comes out clean. Remove cake from oven. Reduce oven temperature to 325°.
To prepare topping, combine syrup, brown sugar, and 2 tablespoons butter in a 4-cup glass measure. Microwave at high 1 minute. Stir with a whisk until butter melts. Whisk in pecans and beaten egg.
Using a wooden skewer, poke holes in top of warm cake. Pour pecan mixture over top of cake. Return cake to oven; bake at 325° for 10 minutes. Cool completely on wire rack.