Melt 1/2 cup butter; pour evenly into 2 (9-inch) round cake pans. Sprinkle brown sugar evenly over butter. Top sugar in each pan evenly with pineapple and pecans. Set pans aside.
Beat remaining 1/4 cup butter and shortening at medium speed with an electric mixer until fluffy. Gradually add granulated sugar, beating well. Add eggs, 1 at a time, beating until blended after each addition.
Combine flour, baking powder, and salt; add to shortening mixture alternately with milk, beginning and ending with flour mixture. Beat at low speed until blended after each addition. Stir in vanilla. Spoon batter evenly over pineapple mixture in prepared pans.
Bake at 350° for 40 minutes or until a wooden pick inserted in center comes out clean. Cool in pans on wire racks 10 minutes; invert onto wire racks to cool completely.
Place 1 cake layer, pineapple side up, on a serving plate. Spread top with 1/2 cup Whipped Cream Frosting. Place remaining layer, pineapple side up, on top. Spread top and sides of cake with remaining Whipped Cream Frosting.