01 - 
                Line an 8x8 inch baking pan with parchment paper, leaving overhang for easy removal. Preheat oven to 350°F.
              
              
              
                02 - 
                In a microwave-safe bowl, melt butter and chopped chocolate in 30-second intervals, stirring after each until smooth and glossy.
              
              
              
                03 - 
                Whisk sugar into the warm chocolate mixture until blended. Beat in eggs one at a time, mixing thoroughly after each. Stir in vanilla extract, white vinegar, and red gel coloring until uniform.
              
              
              
                04 - 
                In a separate bowl, sift together cocoa powder, flour, and salt to remove lumps.
              
              
              
                05 - 
                Add dry ingredients to wet mixture gradually. Fold gently with rubber spatula just until no flour streaks remain, avoiding overmixing.
              
              
              
                06 - 
                Pour batter into prepared pan, smoothing surface. Bake 25-30 minutes until toothpick inserted in center comes out with few moist crumbs.
              
              
              
                07 - 
                Cool completely in pan to set texture. Lift out using parchment overhang and cut into squares with sharp knife, cleaning blade between cuts.