Pour the cake and pudding mix into a large mixing bowl.
Add water, oil and eggs. Mix until just combined.
Pour into cake pan and bake at 350 degrees for 25-30 minutes.
When the cake is finished, remove from oven and let cool slightly.
Poke 12 holes in the cake using the handle of a large round spoon.
Mix the lemon pudding, milk and powdered sugar. Stir until all ingredients are well combined. Pour half of the pudding over the top of the cake, making sure it sinks into all of the holes.
Mix the remaining pudding until it thickens completely then spread over the top of the cake. Place in the refrigerator for 3-4 hours until completely set and chilled.