01 - In a large bowl, whisk together flour, sugar, baking powder, baking soda, and salt until evenly distributed.
02 - In a separate bowl, whisk buttermilk, eggs, melted butter, and vanilla extract until smooth and fully incorporated.
03 - Gently fold wet mixture into dry ingredients just until combined; avoid overmixing to prevent tough waffles.
04 - Divide batter evenly between two bowls. Add cocoa powder and red food coloring to one bowl; stir until well blended and uniform in color.
05 - Preheat waffle iron according to manufacturer instructions and lightly grease with oil or nonstick spray.
06 - Distribute 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 for a marbled effect.
07 - Close lid and cook until waffles are golden brown, crisp, and cooked through, approximately 3 to 5 minutes per batch.
08 - Serve immediately with cream cheese glaze, maple syrup, or fresh fruit as desired.