Preheat oven to 325 F. Beat butter and shortening at medium speed, or until creamy. Gradually add sugar, beating at medium speed until light and fluffy. Add eggs 1 at a time, beating just until blended after each addition.
Stir together flour, baking powder and salt. Add to butter mixture alternately with milk, beginning and ending with flour mixture. Beat at low-speed just until blended after each addition. Stir in vanilla, lime jello . Pour batter into a greased and floured 10-inch (12-cup) tube pan.
Bake at 325 for 1 hour and 15 minutes to 1 hour and 20 minutes (depending on your oven), or until a long wooded pick inserted in the center of cake comes out clean. Cool in pan on a wire rack 10 to 15 minutes, remove from pan to a wire rack.
Prepare Key Lime Glace, and immediately brush over top and sides of cake. Cool completely (about 1 hour).
Key Lime Glaze
1 cup confectioner sugar
2 Tablespoons lime juice
1/2 teaspoon vanilla
1 pack of lime jello
Mix all ingredients together and brush over top and sides of cake.