01 - Whisk together flour, sugar, baking powder, baking soda, and salt in a large bowl until thoroughly combined.
02 - In a separate bowl, whisk buttermilk, eggs, melted butter, and vanilla extract until smooth and homogeneous.
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 uniformly red. Leave second bowl plain for vanilla batter.
05 - Preheat waffle iron according to manufacturer instructions. Lightly grease with oil or nonstick cooking spray.
06 - Spoon alternating dollops of red velvet and vanilla batters onto center of hot iron. Use 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 to 5 minutes per batch.
08 - Serve immediately with cream cheese glaze, maple syrup, or fresh fruit as desired.