Beat butter at medium speed of an electric mixer until creamy; gradually add sugar, beating well. Add eggs, one at a time, beating after each addition.
Combine buttermilk and orange juice. Combine flour and next 6 ingredients; add to butter mixture alternately with buttermilk mixture, beginning and ending with flour mixture. Mix at low speed after each addition until blended. Stir in pecans and next 3 ingredients. Pour batter into 3 greased and floured 9" round cakepans.
Bake at 350° for 25 to 28 minutes or until a wooden pick inserted in center comes out clean. Cool cake in pans on wire racks 10 minutes; remove layers from pans and let cool completely on wire racks.
Spread Seven-Minute Frosting between layers and on top and sides of cake. Sprinkle with coconut. Garnish, if desired.