Preheat oven to 325°F and grease or line a 9x5 loaf pan with parchment paper
In a medium bowl, whisk together the flour, baking soda, salt, and cinnamon. Set aside
In a large bowl, cream the softened butter, brown sugar, and granulated sugar until light and fluffy, about 2 to 3 minutes
Beat in the eggs, then mix in the sour cream, vanilla extract, and mashed bananas
Add the dry ingredients to the wet mixture, folding gently until almost combined
Toss the diced strawberries with 1 tbsp of flour, then carefully fold them into the batter. Do not overmix
Pour the batter into the prepared loaf pan
Bake for 75-85 minutes, or until a toothpick inserted in the center comes out with just a few moist crumbs. Tent with foil around the 45-minute mark if the top is browning too quickly
Let the loaf cool in the pan for 15-20 minutes, then transfer to a wire rack to cool completely before slicing
