Preheat the oven to 350°F (roughly 180°C) and line 2 loaf tins with parchment paper and spray with baking spray then set aside.
In a medium bowl, mash 4 large (roughly 450g) overripe bananas and mix with 1 Tbsp of lemon juice. Set aside.
In a large bowl beat together 1/2 cup (113g) of room temperature unsalted butter, 1/2 cup (100g) of light brown sugar and 3/4 cup (160g) of granulated sugar with a mixer for 2-3 minutes or until light and fluffy.
Add 3 large eggs (150g), 1/3 cup (85ml) of milk, 1/2 cup (135g) of sour cream and the mashed bananas all at room temperature and mix them until combined.
Add in 2 1/2 cups (325g) of cake flour, 1 Tbsp of baking powder, 1/2 tsp of baking soda and 1 tsp of salt and mix carefully making sure not to overmix.
Add half the batter to each loaf tin. Optionally you can sprinkle them with coarse sugar before baking. Bake for 45-55 minutes taking them out when a toothpick inserted in the middle comes out mostly clean.
Allow to loaves to cool for about 45 minutes, then cut, serve with a little bit of butter and enjoy!