Preheat oven to 325 F.
Line an 8 x 8 glass dish with greased parchment paper.
In a large bowl cream together butter, white sugar and brown sugar.
Mix in egg.
Mix in buttermilk, vinegar and vanilla. (Batter will be speckled).
Add food coloring and mix to combine.
Mix in unsweentened cocoa powder.
Add flour and salt.
Mix until smooth and well combined, being sure to scrape down the sides of the bowl.
Pour batter into prepare pan.
Bake for 30-35 minutes or until center is set and toothpick inserted into center comes out clean.
Remove brownies and let cool. (I place mine in the fridge when they are warm to speed up cooling.)
Cut brownies into small squares.
Drizzled with melted white chocolate or cream cheese icing and sprinkle with walnuts (optional)
Store in airtight container