Heat oven to 350. Grease bottom and sides of 2 loaf pans (9 x 5 x 3)
Prepare brown sugar filling and set aside.
Beat together sugar, butter, vanilla & eggs in large bowl with electric mixer on medium for 2 minutes.
Mix flour, baking powder, baking soda and salt. Beat flour mixture and sour cream alternately into sugar mixture on low speed until blended.
Spread 1/4 of the batter (about 1-1/2 cups) into each pan, then sprinkle each with 1/4 of the filling; top with another 1/4 of the batter, and then top with 1/4 of the filling.
Bake for about 60 minutes or until toothpick inserted near center comes out clean. Cool slightly; remove from pans and place top side up on wire rack.
Let cool completely, then wrap up and take to your friends, or eat the whole loaf by yourself (no judgments here).