I've never heard of it but I found this one. Is it similar?

Here is a link that might be useful: Hillbilly cake

Not sure which Hillbilly Cake you are looking for but here are a couple more.

Ann

Hillbilly Cake

Source: www.recipes-from-friends.com

Ingredients:
1 yellow cake mix
1 stick margarine, softened
1 egg
8 oz cream cheese
2 eggs
1 tsp vanilla

Directions:
Mix cake mix, margarine and egg; press into lightly greased 9x11 pan
Mix cream cheese, vanilla and eggs
Pour over mixture in pan
Bake 40 minutes or until set at 350°

HILLBILLY COFFEE CAKE

Source: Cooks.com

1/4 lb. melted butter
1 c. sugar
2 c. flour
1 tsp. baking powder
1 tsp. baking soda
1/4 tsp. salt
1 tsp. vanilla

Mix everything together. Grease and flour a bundt pan. Put half the batter in the pan. Make a mixture of 1/4 cup sugar, 1/2 cup chopped nuts, and 1 teaspoon cinnamon. Sprinkle half the sugar mixture on the batter, then put the rest of the batter in and sprinkle the rest of sugar mixture on top. Bake at 375 degrees for 35-40 minutes. This is a GOOD coffee cake.

I found mine and will share it with you:
HILLBILLY CAKE
1 C sugar
1 C water
1 C raisins
1/2 C butter
1 tea each: cinnamon, allspice and cloves
Put in a pan large enough to mix cake in. Bring to a boil Cook 1 min. Set aside to cool for 20 mins.
Add 2 C flour
1 tea each: baking soda, baking powder
1/1 C chopped nuts
Bake at 350 for 30 mins

Frosting:
1/2 C melted butter
1 C brown sugar
1 C cocoanut
3 TBS cream
Mix and spread over hot cake.
Broil 2-3 mins.

Glad the original turned up!