Cream together butter and sugar. Mash bananas. Add lemon juice to mashed bananas. Beat eggs. Add eggs and crushed bananas, to the creamed butter and sugar. Combine well. Sift together flour, baking powder, and salt. Add to creamed mixture. Add vanilla. Pour into greased loaf pan. Bake at 350 degrees for 60 minutes. Keeps well, refrigerated. Yield 1 Loaf.