Beat butter and shortening at medium speed with an electric mixer until creamy. Gradually add 3 cups granulated sugar, beating at medium speed until light and fluffy. Add eggs, 1 at a time, beating after each addition just until yellow disappears.
Combine flour, salt, and baking powder; add to butter mixture alternately with milk, beginning and ending with flour mixture. Beat at low speed just until blended after each addition, scraping bottom and sides of bowl as needed. Beat in extracts. Pour batter into a greased and floured 12-cup Bundt pan.
Bake at 325° for 1 hour and 5 minutes or until a wooden pick inserted in center comes out clean. Cool in pan on a wire rack 15 minutes. Remove from pan; cool completely on wire rack. Dust cake evenly with powdered sugar.