Prep the pans: Preheat the oven to 350°F (175°C). Grease and line two 8-inch (20 cm) round cake pans with parchment paper. Lightly dust with cocoa powder to prevent sticking.

Mix dry ingredients: In a large bowl, whisk together flour, cocoa powder, sugar, baking powder, baking soda, and salt until no lumps remain.

Add wet ingredients: Add eggs, buttermilk, oil, and vanilla. Whisk until smooth and well combined, about 30–45 seconds.

Add hot liquid: Pour in the hot water or hot coffee. Stir carefully. The batter will be thin—this is normal and helps create a moist cake.

Divide and bake: Pour batter evenly into the pans. Bake for 28–34 minutes, or until a toothpick comes out with a few moist crumbs.

Cool completely: Let cakes cool in the pans for 10 minutes, then turn out onto a wire rack. Peel off parchment and cool fully before frosting.

Make the frosting: In a mixing bowl, beat the butter until fluffy, 2–3 minutes. Sift in powdered sugar and cocoa. Add vanilla, salt, and 3 tablespoons cream. Beat on low to combine, then on medium-high until smooth and creamy. Add more cream, 1 teaspoon at a time, if needed for a spreadable texture.

Assemble: Place one cake layer on a stand or plate. Spread a generous layer of frosting on top. Add the second layer and coat the entire cake with a thin “crumb coat.” Chill 15 minutes.

Finish and decorate: Apply the final layer of frosting. Smooth the sides and swirl the top. Add sprinkles, candies, or themed toppers. Keep it fun and simple.