1️⃣ Preheat the Oven: Preheat your oven to 350°F (175°C). Line an 8×8-inch baking pan with parchment paper, leaving an overhang for easy removal, or grease the pan thoroughly.

2️⃣ Prepare Red Velvet Brownie Batter:
In a large bowl, whisk together the melted butter and sugar until well combined. Add the eggs, vanilla extract, red food coloring, and white vinegar, and continue whisking until smooth.
Sift in the flour, cocoa powder, and salt, then gently stir until just combined (avoid over-mixing to keep the brownies tender). Pour most of the batter into the prepared baking pan, reserving about ¼ cup for swirling.

3️⃣ Make Cheesecake Swirl:
In a medium bowl, beat the softened cream cheese with sugar until smooth. Add the egg and vanilla extract, mixing until the cheesecake mixture is creamy and free of lumps.

4️⃣ Assemble the Swirl:
Spread the cheesecake mixture evenly over the red velvet brownie layer in the baking pan. Drop spoonfuls of the reserved red velvet batter on top, then use a knife or toothpick to gently swirl the brownie and cheesecake layers together, creating a marbled effect.

5️⃣ Bake:
Bake for 25-30 minutes, or until the center is set and a toothpick inserted into the brownies comes out mostly clean (a few moist crumbs are fine). Be careful not to overbake to keep the brownies fudgy.

6️⃣ Cool and Serve:
Allow the brownies to cool completely in the pan before lifting them out using the parchment overhang. Slice into squares and enjoy the delicious mix of red velvet and cheesecake flavors!