Preheat the oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.

In a mixing bowl, combine flour, sugar, cocoa powder, baking powder, baking soda, and salt.

Add buttermilk, vegetable oil, eggs, and vanilla extract. Mix until smooth.

Divide the batter evenly between the prepared pans.

Bake for 30 minutes or until a toothpick inserted in the center comes out clean.

Let the cakes cool in the pans for 10 minutes, then transfer to wire racks to cool completely.

Once the cakes are cool, place one layer on a serving plate.

Spread half of the caramel sauce over the first layer, then sprinkle with half of the chopped peanuts.

Place the second layer on top and repeat the process with the remaining caramel and peanuts.

In a mixing bowl, beat the softened butter until creamy. Gradually add powdered sugar and heavy cream, beating until fluffy. Stir in vanilla extract.

Frost the top and sides of the cake with the buttercream frosting.

Top with remaining chopped peanuts and drizzle with caramel sauce.