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, spooned and leveled, 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 cold or melted 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, cold, cut into cubes (or you can use melted, sometimes that’s easier)
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 Heaping 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 some of the cinnamon sugar mixture in the middle, reserve a little to garnish on the top after it bakes. (You can swirl it in with a knife if you want or just leave it in a layer is what I usually do), 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. If you notice the tops browning too quickly, you can tent with foil.
Allow the bread to cool in the pan for about 15-30 minutes and then invert onto a cooling rack. Whisk together the ingredients for the glaze and drizzle it over the top of the cooled bread. Garnish with any leftover cinnamon/sugar. Slice and enjoy!
1 cup powdered sugar, 1-2 Tbsp. milk, 1 tsp. vanilla extract, pinch salt