01 - Whisk together flour, sugar, baking powder, baking soda, and salt in a large bowl until evenly combined.
02 - In a separate bowl, whisk buttermilk, eggs, melted butter, and vanilla extract until smooth and fully incorporated.
03 - Gently fold the wet mixture into the dry ingredients just until combined. Take care not to overmix to maintain tender texture.
04 - Divide batter evenly between two bowls. Add cocoa powder and red food coloring to one bowl; stir until well blended and uniform red color achieved. Leave remaining batter plain for vanilla contrast.
05 - Heat waffle iron according to manufacturer instructions. Lightly grease cooking surface with oil or nonstick spray.
06 - For each waffle, dollop alternating spoonfuls of red velvet and vanilla batters onto the center of the hot iron. Use a chopstick or butter knife to gently swirl batters together for marbled effect.
07 - Close lid and cook until waffles are golden brown, crisp, and cooked through, approximately 3–5 minutes per batch.
08 - Serve immediately while warm. Accompany with cream cheese glaze, maple syrup, or fresh fruit as desired.