Preheat oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan. In a medium bowl, whisk together the flour, baking powder, and salt. Set aside the dry ingredients.
In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy. This usually takes 2-3 minutes with an electric mixer.
Beat in the eggs one at a time, mixing well after each addition.
Gradually add the vegetable oil and vanilla extract to the wet ingredients, mixing until just combined.
Alternately add the dry ingredients and milk to the wet ingredients, beginning and ending with the dry ingredients. Mix on low speed until just combined. Be careful not to overmix.
Pour the batter into the prepared baking pan and spread evenly.
Bake for 30-35 minutes, or until a wooden skewer inserted into the center comes out clean.
Let the cake cool in the pan for 10-15 minutes before adding jello
In a small bowl, dissolve the orange gelatin in the hot water, stirring until completely smooth and no granules remain.
Lightly poke the cake and pour the jello over top
Once the cake is completely cool, frost it with the thawed whipped topping. Spread an even layer over the top of the cake.
Store the frosted cake in the refrigerator.