Heat oven to 350°F. Spray three 8-inch round cake pans with nonstick cooking spray. (You could also use the butter and flour method, line with parchment paper, or use GOOP*.)
In a medium bowl, sift together flour, baking soda, and salt. Set aside.
To the bowl of a stand mixer, add bananas, lemon juice, butter, sugar, and vanilla. Mix until incorporated and smooth. (You could also use a handheld mixer.)
Add in eggs, one at a time, beating well after each addition.
With mixer on low, add flour mixture to banana mixture alternativly with buttermilk, beginning and ending with flour mixture.
Mix until just combined.
Pour batter into the three prepared 8-inch round baking pans.
Bake for 28-32 minutes, or until the center no longer appears wet and an inserted toothpick is removed with a few crumbs.
Cool in pans on a wire rack for 10 minutes. Then, remove the cakes and place them on a wire rack to cool completely before assembly.