Heat oven to 350°F. Grease 2 (8- or 9-inch) round cake pans with shortening; lightly flour. Line bottom of pans with waxed paper. In medium bowl, mix flour, sugar, baking soda, salt and baking powder; set aside.
In large bowl, beat remaining cake ingredients with electric mixer on medium speed until well blended, scraping bowl occasionally. On low speed, beat in flour mixture until moistened, scraping bowl occasionally. Beat on high speed 3 minutes, scraping bowl occasionally. Pour batter evenly into pans.
Bake 30 to 40 minutes or until toothpick inserted in center comes out clean. Cool in pans 10 minutes. Remove from pans; place on wire racks. Cool completely, about 1 hour.
In small bowl, beat frosting ingredients with electric mixer on low speed until moistened. Beat on high speed until smooth and creamy. Place 1 cake layer, top side down, on serving plate. Spread evenly with about 1/4 of frosting. Top with remaining cake layer, top side up. Spread sides and top of cake with remaining frosting.