Preheat oven to 350 degrees F (175 degrees C). Grease one 8x8 inch square pan.
Cream the butter or margarine add the sugar and continue creaming until light and fluffy. Beat in the eggs one at a time. Stir in the maple flavoring.
Combine the flour, baking powder, and salt. Add the flour mixture in 3 parts alternately with the milk to the butter mixture, beginning and ending with flour. Stir in the walnuts and pour in the prepared pan.
Bake at 350 degrees F (175 degrees C) for 40 to 45 minutes or until an toothpick inserted in the center comes out clean. Let cake cool then frost with Maple Butter Icing.
