Preheat your oven to 350°F (175°C) and line an 8x8 inch baking pan with parchment paper.
Melt the unsalted butter and chopped semi-sweet chocolate together in a large microwave-safe bowl.
Add granulated sugar to the melted mixture and stir until well combined. Beat in the eggs one at a time, then stir in vanilla extract, white vinegar, and red gel food coloring.
In a separate bowl, sift together unsweetened cocoa powder, all-purpose flour, and salt.
Gradually add the dry ingredients into the wet mixture while stirring gently until just combined. Optionally fold in white chocolate chips.
Pour the brownie batter into the prepared baking pan and bake for 30-35 minutes or until a toothpick comes out with a few moist crumbs.