Preheat the oven to 350°F and grease a 9x5 inch loaf pan. (I recommend using a light colored aluminum pan because they enable even, controlled heat resulting in a gentle heat and tender crumb. This bread has not been tested in a glass pan). I like to brush the pan with a little softened butter and sprinkle an even layer of flour around the pan. Set aside.
Whisk the dry ingredients together in a medium mixing bowl and set aside.
2 cups all purpose flour, 1 tsp. baking soda, 1/2 tsp. salt, 1/2 tsp. cinnamon
Combine the sugar and cinnamon in a small dish for the swirl and set aside.
1/4 cup granulated sugar, 1 Tbsp. ground cinnamon
For the streusel combine the flour, brown sugar and cinnamon. Add the butter and mix until the mixture clumps together, I use my fingers but two forks or a pastry cutter works too.
3/4 cup all purpose flour, 1/2 cup brown sugar, packed (light or dark), 1 Tbsp. ground cinnamon, 5 Tbsp. unsalted butter, cut into cubes
Mash the bananas in a large bowl and add in the remaining wet ingredients. Beat with a hand mixer to combine.
3 medium over ripe bananas, mashed (1 1/4 cup), 1/2 cup canola oil, 1/2 cup granulated sugar, 2 large eggs, room temperature, 1/4 cup sour cream, room temperature, 1/4 cup buttermilk, 2 tsp. vanilla extract, 1/2 cup brown sugar, packed (light or dark)
Fold in the dry ingredients and mix just until combined.
Pour 1/2 of the banana bread mixture into the prepared loaf pan, sprinkle the cinnamon sugar mixture in the middle (you can swirl it in with a knife if you want), and then pour the remaining banana bread batter on top. Top with the streusel.
Bake for ~55 minutes or until a toothpick inserted in the center comes out clean, a few crumbs are okay but it shouldn't look wet.
Allow the bread to cool in the pan for 30 minutes and then invert onto a cooling rack. Whisk together the ingredients for the glaze and drizzle it over the top of the bread. Slice and enjoy!
1 cup powdered sugar, 2-3 Tbsp. milk, 1 tsp. vanilla extract, pinch salt