01 - Preheat oven to 350°F. Grease and flour a 9x5-inch loaf pan or line with parchment paper.
02 - In a bowl, mix flour, brown sugar, cinnamon, and salt. Pour in melted butter and stir until crumbly. Set aside.
03 - In a medium bowl, whisk together flour, baking soda, salt, and cinnamon for the bread.
04 - In a large bowl, beat butter and sugar together until light and fluffy. Add eggs one at a time, mixing well after each. Stir in vanilla.
05 - Mix in mashed bananas and yogurt or sour cream until just combined.
06 - Gently fold the dry ingredients into the wet mixture until no flour streaks remain—do not overmix.
07 - Pour batter into prepared loaf pan. Evenly sprinkle the cinnamon crumb topping over the batter.
08 - Bake for 50-60 minutes, or until a toothpick inserted in the center comes out clean or with just a few moist crumbs.
09 - Cool in the pan for 15 minutes, then transfer to a wire rack to cool completely before slicing.