Preheat oven to 350°F/180°C. Line an 8×8-inch pan with parchment.
Brownie batter: Microwave butter, cocoa, and salt in 30-second bursts, stirring between. Mix in sugar, eggs, vanilla, and vinegar. Add food coloring to desired shade. Fold in flour. Set aside ⅓ cup batter, pour rest into pan.
Cheesecake batter: Beat cream cheese and sugar until smooth. Add egg and vanilla, mix well. Dollop over brownie batter.
Spoon reserved brownie batter on top. Swirl batters with a knife for marbling.
Bake 25-30 minutes until cheesecake is set and toothpick comes out with moist crumbs. Cool completely, then chill 2+ hours until firm. Lift out with parchment and cut into squares.
Notes
Ensure your cream cheese and eggs are at room temperature for a smoother cheesecake layer. This helps achieve a creamy texture without lumps.
Food Coloring: If you're going for a vibrant red color, gel food coloring is the best choice, as it doesn’t add extra liquid to the batter. You can adjust the amount based on your preference for color intensity.
Swirling Technique: When swirling the batters, try to create a figure-eight motion with the knife to get a beautiful marbling effect without overmixing.
Baking Time: Ovens can vary, so start checking for doneness a few minutes before the minimum baking time. Look for the cheesecake to be set but still slightly jiggly in the center.
Serving Suggestions: These brownies pair wonderfully with a dollop of whipped cream or a scoop of vanilla ice cream. A drizzle of chocolate or cream cheese frosting can also elevate the presentation!
Customization: Feel free to add chocolate chips to the brownie batter or a sprinkle of sea salt on top before baking for an extra flavor dimension. Storage Tips: To keep them fresh, store the brownies in an airtight container in the fridge. You can also freeze them for up to 2 months—just thaw in the fridge before enjoying!
Garnishing: Consider topping the brownies with crushed walnuts or pecans for a crunchy contrast to the creamy layers.Store in fridge up to 5 days. They're even better the next day!