Step 1
Preheat oven to 350 degrees F (175 degrees C). Grease the base and sides of a 10-inch fluted tube pan. Dust lightly with flour; tap to remove excess.
Step 2
Fill a shallow baking pan with enough water to come 1/3 of the way up the sides of the tube pan. Place water bath in the oven to warm up while it is preheating.
Step 3
Pour caramel sauce into a microwave-safe bowl. Microwave until warm and pourable about 1 minute. Pour into the prepared tube pan covering the base completely.
Step 4
Mix flour cocoa powder baking soda and baking powder together in a bowl.
Step 5
Beat 1/2 cup plus 2 1/2 tablespoons butter in a bowl with an electric mixer until smooth. Add sugar; beat until light and fluffy. Beat in 1 egg and coffee. Alternate adding flour mixture and milk mixing well between additions. Pour cake batter evenly over caramel in the tube pan.
Step 6
Combine evaporated milk condensed milk 4 eggs and vanilla extract in the bowl of a food processor; blend until smooth. Pour over cake batter through a fine sieve.
Step 7
Bake in the water bath in the preheated oven until a toothpick inserted into the chocolate cake comes out clean about 1 hour.
Step 8
Let cake cool about 1 hour. Carefully run a thin knife around the edges to loosen the cake cover with a serving plate and flip onto the plate.