In mixing bowl, cream brown sugar and butter together until creamy, add one egg at a time until well incorporated, add vanilla, bananas, sour cream (or yogurt or buttermilk) scrap down the sides of the bowl and continue to mix on low speed.
In separate bowl sift dry ingredients together. Add to the wet mix and combine until no streaks of dry ingredients are visible.
Fold in the nuts.
Pour batter into a greases/floured 10 cup bundt pan and bake in a 350 degree preheated oven for 30-50 minutes (depending on oven), begin checking for doneness at 30 minutes with a toothpick. Toothpick should come out clean when piercing the center of cake.
Cool in pan for 10 minutes before turning out on a rack to finish cooling.