Cream butter and sugar; stir in eggs and lemon extract. Add bananas and mix well. In a separate container combine flour, baking powder and salt. Add gradually to sugar mixture, mixing well. Fold in peanuts. Pour batter into a greased 8-1/2 x 4-1/2 inch loaf pan. Bake at 350° F. for one hour or until a cake tester comes out clean. Allow to cool in pan about 30 minutes before turning onto a rack. Freezes well.