How to Make Moist and Delicious Red Velvet Brownies

1/2 cup (112g) unsalted butter
1 tbsp vegetable oil
3/4 cup (150g) sugar
1/2 tsp salt
2 eggs
1 tsp white vinegar
1 tsp vanilla
1 tsp red food coloring
3/4 cup (98g) all purpose flour
2 tbsp (14g) cocoa powder