Beat butter and shortening at medium speed with an electric mixer until creamy. Gradually add sugar, beating at medium speed until light and fluffy. Add eggs, 1 at a time, beating just until the yellow yolk disappears.
Sift together flour, baking powder, and salt; add to butter mixture alternately with milk, beginning and ending with flour mixture. Beat batter at low speed just until blended after each addition. Stir in vanilla and lemon extracts. Pour batter into a greased and floured 12-cup tube pan.
Bake at 325° for 1 hour and 30 minutes or until a long wooden pick inserted in center of cake comes out clean. Cool in pan on a wire rack 10 to 15 minutes. Remove from pan; carefully brush Lemon Curd over top and sides of cake. Cool completely on wire rack. Garnish, if desired.