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

In a large bowl, whisk together flour, cocoa powder, baking soda, sugar, and salt.

In another bowl, mix melted butter and sugar until creamy. Beat in eggs one at a time. Stir in buttermilk and vanilla.

Gradually fold dry ingredients into wet mixture until combined. Optionally add chocolate chips.

Divide batter between pans and bake for 30-35 minutes or until a toothpick comes out clean.

Cool in pans for 10 minutes before transferring to wire racks to cool completely. Frost as desired.