Lemon Sweetened Condensed Milk Cake

1 (18.25 ounce) box yellow cake mix (butter recipe)
1 (14 ounce) can sweetened condensed milk
Juice of 3 lemons

Bake cake in two 9-inch pans as directed on box.

Combine sweetened condensed milk and lemon juice. Spread half of mixture over bottom layer. Place top layer on and spread remaining mixture on top.