1For the cake: Preheat oven to 350. Spray 9x12x2" sheet cake pan. In a lg mixing bowl, mix the gelatin, sugar and flour. Stir to mix well. Add the oil, orange juice, lemon juice, vanilla and eggs. Mix until well combined. The mix will be runny. Pour the batter evenly into the pan and bake for 35-40 minutes. Insert toothpick in the middle to check for doneness. Cool the cake in the pan for 5 minutes then turn out onto a cooling rack.
2For the glaze: While the cake is still hot, mix the lime juice and the confectioner's sugar until well combined. Prick the cake with a fork and pour the glaze all over the top. Cool completely.
3For the icing:
cream the butter and cream cheese. Beat in the confectioner's sugar and zest til mixture is smooth and easy to spread. Spread the icing on the top and sides of the cake.
4I actually made some sugared lime twists to put on top for decoration, which were tasty as well.