01 - Preheat oven to 350°F. Grease a 9x13-inch baking pan and line with parchment paper.
02 - In a large bowl, whisk together flour, sugar, baking powder, baking soda, cocoa powder, and salt until well combined.
03 - In a separate bowl, whisk buttermilk, vegetable oil, eggs, vanilla extract, white vinegar, and red food coloring until smooth.
04 - Pour wet ingredients into dry ingredients. Fold gently just until combined—avoid overmixing to maintain tender texture.
05 - Transfer red velvet batter to prepared pan, spreading evenly across the bottom with an offset spatula.
06 - Beat softened cream cheese until smooth and creamy. Add sugar, egg, and vanilla; mix until fully incorporated and lump-free.
07 - Drop spoonfuls of cheesecake mixture over the red velvet batter. Run a knife or skewer through both batters in a figure-eight motion to create marbled pattern.
08 - Bake for 45-50 minutes until a toothpick inserted into the center emerges mostly clean—traces of cheesecake are acceptable.
09 - Let cake cool completely in the pan on a wire rack before slicing to ensure clean cuts and proper texture.