Preheat oven to 350 degrees F. Mist two 9-inch cake pans with nonstick cooking spray. If desired for ease of cake removal, cut a 9-inch diameter circle out of parchment paper to set in the bottom of each prepared cake pan. Mist parchment with nonstick cooking spray and set aside.
In a large bowl, whisk together the flour, baking soda, and cinnamon together. Set aside.
Using an electric mixer beat butter and sugar until well combined. Add the eggs and the vanilla. Beat on medium-high until combined, then add in the mashed bananas and continue beating. Scrape down the sides and bottom of the bowl as needed. With the mixer on low speed, add half of the dry ingredients alternating with the buttermilk and mixing each addition until just incorporated.
Evenly divide the batter into prepared cake pans and spread evenly to reach the sides, smoothing out the top.
Bake in preheated oven 25-30 minutes, until a toothpick inserted into the center, comes out clean. Allow cakes to cool completely then frost with Banana Cream Cheese Frosting.
To make the frosting, in the bowl of an electric mixer beat the butter on high until creamed. Add the cream cheese and continue beating on high until smooth and creamy. Add banana, vanilla, lemon juice, salt, and sugar; beat on low for 30 seconds, then on high until light and fluffy, about 2 minutes.
Place 1 of the cakes on a dish or cake stand. Top with about ⅓ of the frosting, spreading to the edges. Top with the second cake and spread the remaining frosting over the top and sides of the frosting. If frosting is too thin, refrigerate for 15 minutes. Garnish with nuts, as desired.
Refrigerate for at least 30 minutes before serving. Leftover cake should be covered and stored in the refrigerator for up to 5 days.