Tres Leches Cake

1 package (18.25 ounces) white cake mix
3 eggs
1 1/4 cups water
1 can (12 ounces) evaporated milk
1 container (8 ounces) sour cream or 4 ounces sour cream and 4 ounces whipping cream
1/2 cup sweetened condensed milk
1 tsp vanilla
1 container (8 ounces) Cool Whip, thawed
1/4 tsp cinnamon

Preheat oven to 350F. Spray 9 inch square pan with 1 1/2 inch high side. Mix cake mix, eggs and water well. Pour into pan and bake for 35 to 40 minutes until knife comes out clean. Cool.
Slice top of cake off horizontally. Mix evaporated milk, condensed milk, sour cream and vanilla and pour over cake. Spread the Cool Whip on top of cake.