Heat oven to 350°F for shiny pans or 325°F for dark nonstick pans. Grease and flour 2 9-inch round cake pans. In food processor, combine beans and 1/4 cup of the buttermilk. Cover; process 30 seconds or until smooth. In large bowl, combine bean mixture, 1/4 cup of the butter, the granulated sugar, eggs and gelatin. Beat with electric mixer on low speed until mixed. Beat on medium speed 1 minute. Add flour, baking powder, baking soda and salt. Beat on low speed until mixed. On low speed, add remaining 3/4 cup buttermilk; beat until mixed. Beat on medium speed 2 minutes. Divide evenly between pans (about 3 cups batter per pan).
Bake 28 to 33 minutes or until top is set when tapped with a finger and toothpick inserted in center comes out clean. Cool in pans 10 minutes. Remove from pans to cooling racks. Cool completely, about 45 minutes.
In large bowl, combine remaining 1/4 cup butter, the cream cheese, powdered sugar, lemon peel and 3 tablespoons of the lemon juice. Beat with electric mixer on low speed until mixed. Beat on medium speed until smooth and creamy, adding additional lemon juice until desired consistency. Place one cake layer on cake plate, rounded side down. Spread top with frosting. Place remaining cake layer over frosting, rounded side up. Frost top and sides of cake. Store loosely covered.