Sift together flour, baking powder, soda, salt and cinnamon. Beat eggs and add sugar. Let stand until sugar dissolves, about 10 minutes. Stir in oil, carrots, drained pineapple and nuts. Turn into 3 greased and floured 9-inch round cake pans or 1 (13x 9-inch) pan and bake at 350F 35 to 40 minutes for layer pans and about 55 minutes for 13x 9-inch pan, or until cake springs back when lightly touched. Cool in pans about 10 minutes, then turn onto wire racks to cool completely. To make frosting, combine butter, cream cheese and vanilla in large bowl and beat until well blended. Add powdered sugar gradually, beating vigorously. If too thick, thin with milk to spreading consistency. Frost between layers, top and sides of layer cake. Frost top and sides of sheet cake.