Cream butter; gradually add sugar, beating well. Add egg yolks, one at a time, beating well after each addition.
Dissolve soda in buttermilk; add to creamed mixture alternately with flour, beginning and ending with flour. Stir in mashed bananas and pecans.
Beat egg whites (at room temperature) until stiff peaks form: fold into batter.
Pour batter into 2 greased and floured 8-inch round cake pans. Bake at 350° for 30 minutes or until a wooden pick inserted in center comes out clean. Cool cake in pans 10 minutes; remove layers from pans, and let cool completely.
Spread Caramel Frosting between layers and on top and sides of cooled cake.