Preheat the oven to 350°F (175°C). Grease two 8×4 inch pans.

In a small bowl, mash the bananas, brown sugar, vanilla extract, and ground cinnamon until well combined.

In a large bowl, cream together the softened butter and sugar until light and fluffy.

Add in the eggs one at a time, mixing well after each addition.

Sift in the all-purpose flour, baking soda, and salt, then stir until just combined.

Add the sour cream or Greek yogurt and mix until fully integrated.

Pour in the banana mixture and gently fold until just combined.

For the crumb topping, combine the flour, brown sugar, cold butter, and cinnamon. Crumble together until the mixture resembles coarse crumbs.

Pour the banana bread batter into the prepared pans and sprinkle the crumb topping generously over the surface.

Bake in the preheated oven for 50-60 minutes, or until a toothpick inserted in the center comes out clean.

Allow to cool for 10 minutes in the pans, then transfer to a wire rack to cool completely.