Pumpkin pie cake

Tried this at work and it was very tasty.

1-29 oz can pumpkin (I used 2-15 oz cans)
1-12 oz can evaporated milk
3 eggs
1 cup sugar
4 tsp pumpkin pie spice (I doubled the cinnamon, cloves, and ginger on pumpkin pie recipe)
yellow cake mix
1/2 cup melted butter

Preheat oven to 350 degrees. Mix the first five ingredients until smooth. Pour into greased 9x13 pan. Sprinkle cake mix evenly over the top. Drizzle butter on top of cake mix. Bake for 45-50 minutes, until knife comes out clean. Drizzle with cream cheese icing. Enjoy!