01 - Preheat oven to 350°F. Grease a 9x13-inch baking pan and line with parchment paper.
02 - Whisk together flour, sugar, baking powder, baking soda, cocoa powder, and salt in a large bowl.
03 - In a separate bowl, combine buttermilk, oil, eggs, vanilla, vinegar, and red food coloring. Mix thoroughly.
04 - Pour wet ingredients into dry ingredients. Mix just until combined—avoid overmixing.
05 - Spread red velvet batter evenly in the prepared pan using a spatula.
06 - Beat cream cheese until smooth. Add sugar, egg, and vanilla; mix until creamy and well-blended.
07 - Drop spoonfuls of cheesecake mixture over the batter. Use a knife to swirl gently for a marbled pattern.
08 - Bake for 45–50 minutes until a toothpick inserted into the center comes out clean.
09 - Cool completely in the pan on a wire rack before slicing.