Preheat the oven to 350 degrees F. Line a 9×9 baking pan with parchment paper with overhang for handles. Or line with aluminum foil and spray lightly with baking spray.
In a large microwave-safe bowl melt the butter and bittersweet chocolate for 1 1/2 to 2 minutes, stirring every 30 seconds until completely melted and smooth.
4 oz Bittersweet chocolate bar, 3/4 cup Unsalted butter
Whisk in the sugar.
1 1/2 cup Granulated sugar
Add the eggs, one at a time, whisking until blended after each one. Stir in the flour, baking powder, salt, red food coloring, and vanilla extract.
4 large Eggs, 1 1/2 cup All-purpose flour, 1 1/2 tsp Baking powder, 1 oz Red food coloring, 1/4 tsp Kosher salt, 1 1/2 tsp Vanilla extract
Pour the brownie batter into the prepared pan and bake for 40-45 minutes, or until a wooden skewer or toothpick inserted into the center comes out clean or with just a few moist crumbs.
Remove the pan from the oven to a wire rack to cool completely. Once cooled remove the brownies from the pan to a cutting board.