Step 1: Preheat oven to 350°F (175°C). Grease and flour two 8-inch round cake pans or one 9x13-inch pan. You can also line the bottoms with parchment paper for easier removal.
Step 2: In a large bowl, whisk together the flour, granulated sugar, cocoa powder, baking soda, baking powder, and salt. Ensure there are no lumps.
Step 3: In a separate medium bowl, whisk together the buttermilk, vegetable oil, eggs, and vanilla extract until well combined.
Step 4: Pour the wet ingredients into the dry ingredients. Mix on low speed with an electric mixer (or by hand with a whisk) until just combined. Do not overmix.
Step 5: Carefully pour in the hot coffee (or hot water) into the batter. Mix on low speed until the batter is smooth and well combined. The batter will be thin; this is normal and contributes to the cake's moistness.
Step 6: Divide the batter evenly between your prepared cake pans. For round cakes, this usually means about two cups of batter per pan. For a 9x13-inch pan, pour all the batter in.
Step 7: Bake for 30-35 minutes for round cakes, or 35-40 minutes for a 9x13-inch cake, or until a wooden skewer or toothpick inserted into the center comes out clean or with a few moist crumbs attached.
Step 8: Let the cakes cool in the pans on a wire rack for 10-15 minutes. This allows them to set before inverting. This is a crucial step for this easy moist chocolate cake recipe.
Step 9: Invert the cakes onto the wire rack and remove the pans. Allow the cakes to cool completely before frosting. This ensures your frosting won't melt.