Pre heat oven to 325 degrees F. Grease two 8-inch round cake pans with baking spray with flour. Line bottom of cake pans with a circle of parchment paper.
Mash bananas thoroughly until no chunks remain. You can do this with fork, potato masher, or my favorite the hand held mixer. Measure out 1 1/2 cups of mashed bananas and set aside. I used four medium sized bananas.
In a large bowl, sift together flour, baking powder, baking soda, salt, and cinnamon and set aside.
In the bowl of a stand mixer fitted with the paddle attachment, cream butter and sugars together on medium-high speed until light and fluffy. About 3-5 minutes.
Add eggs, one at a time, and beat well after each addition.
Next, stir in lemon juice, vanilla extract and mashed bananans.
With the mixer on low speed, slowly add flour mixture (flour should be added in 3 rounds and buttermilk in two) alternating with the buttermilk, beginning and ending with the flour mixture. Mix just until combined after each addition, being careful not to overmix. Be sure to scrape down the sides as necessary after each addition. Mix ingredients just until incorporated. At the end, I like to take a large spatula and mix the batter (about 10 strokes) making sure to reach all of the batter at the bottom of the bowl to ensure all the butter is incorportated.
Divide batter evenly into prepared cake pans and bake for 35-45 minutes (mine were done at 45 minutes). Bake until a toothpick inserted into the center comes out clean.
Allow cakes to cool in cake pans for ten minutes on wire rack. Invert and remove cakes from cake pans. Let cake cool completely on wire rack. Do not frost cake until completely cool.