Cream butter; gradually add sugar, beating well. Add eggs, one at a time, beating well after each addition. Add sweet potatoes; beat well.
Combine flour, baking powder, soda, salt, and spices; add to creamed mixture alternately with milk, beginning and ending with flour mixture. Beat well after each addition. Stir in chopped pecans.
Spoon batter into a greased 9- inch square pan. Bake at 350° for 40 minutes or until a wooden pick inserted in center comes out clean. Cool. Spread Brown Sugar Caramel Icing over cake. Cut into squares to serve.