Use both natural and Dutch-process cocoa for depth and classic red hue, and ensure your buttermilk and eggs are at room temperature to prevent a dense crumb. If you prefer a brighter red, increase food coloring slightly, but balance by adding a teaspoon more cocoa for flavor. Coffee should be hot but not boiling when added to avoid scrambling eggs; temper by whisking into the wet mix gradually. For cleaner layers, chill the cakes for 20 minutes before frosting, and warm the offset spatula under hot water for smooth sides. Store covered at room temperature for 1 day or refrigerate up to 4 days, bringing slices to room temperature before serving.