Preheat oven to 350℉. Line bottom and sides of a 9-inch square baking pan with foil, allowing 2 - 3 inches to extend over sides; lightly spray with nonstick cooking spray.
Microwave chocolate and butter in a large microwavable bowl on HIGH until melted (1 1/2 - 2 minutes). Whisk until smooth.
Whisk in sugar.
Add eggs, one at a time, whisking just until blended.
Whisk together flour, baking powder, and salt. Gently stir flour mixture, food coloring, and vanilla into chocolate mixture, stirring just until well incorporated.
Pour batter into prepared pan. Bake in preheated oven until a wooden toothpick inserted in center comes out with a few moist crumbs, about 25 minutes.
Cool completely on a wire rack.
While brownies are cooling, prepare frosting. Beat cream cheese and butter until creamy, but do not overbeat. With mixer on low, add powdered sugar and mix until smooth. Beat in vanilla. Increase speed to high and beat until light and fluffy, just about 1 - 2 minutes.
Cut into squares and serve.
