Preheat oven to 350°F. Grease and flour two 9-inch round baking pans.

In a medium bowl, sift together flour, baking soda, salt, and cocoa powder. Set aside.

In a large bowl, cream butter and sugar together until light and fluffy. Beat in eggs one at a time, then stir in vanilla extract.

Gradually add dry ingredients to the butter mixture, alternating with the buttermilk. Beat until just combined.

Divide the batter evenly between the prepared pans. Bake for 30 to 35 minutes, or until a toothpick inserted into the centre comes out clean.

Let cool in pans for 10 minutes before turning out onto a wire cooling rack to cool completely.

To assemble the cake, place one of the cooled cakes onto a cake board or plate. Spread a thin layer of frosting on top, then place the remaining cake on top of that. Frost the entire cake with your favourite frosting. Enjoy!