Preheat Oven & Prepare Pans: Preheat oven to 350°F (175°C). Grease and flour two 9-inch round cake pans, or grease and line the bottoms with parchment paper.
Combine Dry Ingredients: In a large bowl, sift or whisk together the flour, sugar, cocoa powder, baking soda, baking powder, and salt.
Combine Wet Ingredients: In a separate medium bowl, whisk together the buttermilk, oil, eggs, and vanilla extract.
Mix Batter: Pour the wet ingredients into the dry ingredients and beat with an electric mixer on medium speed for about 2 minutes until well combined. The batter will be thick.
Add Hot Liquid: Carefully pour the hot water or hot coffee into the batter and mix on low speed until just combined. The batter will be thin, which is normal.
Pour & Bake: Pour the batter evenly into the two prepared cake pans.
Bake for 30-35 minutes, or until a wooden toothpick inserted into the center comes out clean or with a few moist crumbs attached.
Cool Cake: Let the cakes cool in the pans for about 15 minutes before inverting them onto a wire rack to cool completely.
Make Frosting: While the cakes cool, prepare the frosting. In a large bowl, beat the softened butter until creamy. Sift in the cocoa powder and beat until combined.
Alternately add the powdered sugar and the milk/cream, beating on low speed until combined, then on high speed until light and fluffy. Stir in the vanilla extract and a pinch of salt.
Assemble & Frost: Once the cake layers are completely cool, place one layer on a serving plate. Spread a generous amount of frosting on top. Place the second layer on top. Frost the top and sides of the entire cake.
Enjoy: Your delicious homemade easy chocolate cake recipe is ready to be sliced and served!