Preheat oven to 350 degrees.
Spray the inside (bottom and sides) of 2 loaf pans with non-stick cooking spray. I used 9"x5"x3" pans. Set pans aside.
In a small mixing bowl, prepare the brown sugar cinnamon filling and set aside.
In a large mixing bowl, beat together sugar, butter, vanilla extract, and eggs with an electric mixer on medium speed for 2 minutes.
In a separate mixing bowl, mix together flour, baking powder, baking soda, and salt.
Alternate adding the flour mixture and the sour cream to the creamed butter/sugar mixture while mixing on a low speed. Combine until just blended (be sure to not overmix).
Pour 1 1/2 cups of the batter into the bottom of each pan (should be about 1/4 of the batter in each pan).
Sprinkle 1/4 cup of the brown sugar filling in each pan on top of the batter.
Top with another 1 1/2 cups of batter in each pan, then divide and sprinkle the remaining brown sugar filling on the batter in each pan.
Bake for 55-65 minutes (start checking it around 55 minutes) until a toothpick inserted in the center of the loaf pan comes out clean.
Let the bread cool in the pans for 5-10 minutes and then remove from pans and let them completely cool on a wire rack.