Preheat the oven to 350 and prepare an 8x8 pan with parchment or grease. Set to the side.
In a large bowl, whisk the melted butter, oil, and sugar in a bowl. Add in the eggs and whisk until the mixture is light and foamy. Add in the vanilla, vinegar, and food dye.
Add the flour, cocoa powder, and salt to the mixture. Gently fold the dry ingredients in until fully combined. Set the batter to the side.
Make the cheesecake swirl. In a medium-sized bowl with a hand mixer or in the bowl of a stand mixer with a paddle attachment, beat the cream cheese, sugar, egg yolk, and vanilla.
Pour the brownie batter into the prepared pan. Then, dollop the creamcheese mixture on top. Use a butter knife or a long skwer to create the swirls. Go back and forth until the desired pattern is acieved.
Bake the brownies in the oven for 25-30 minutes. Let the brownies cool completely in the pan before removing and cutting.
