I always use this caramel frosting recipe to spread over top of baked caramel cake or cupcakes. Use Duncan Hines caramel cake mix to bake the caramel cake.
Quick Caramel Frosting
1 stick (1/2 cup) butter
1 cup light brown sugar, packed
1/4 cup heavy whipping cream
1 to 1 1/2 cups powdered sugar, sifted
Melt butter in a small saucepan over medium heat. Stir in brown sugar and cook until sugar is completely dissolved. Add the cream and let mixture boil. Cool slightly, then beat in enough powdered sugar until desired spreading consistency. Perfect too with a baked vanilla chiffon cake.