Preheat oven to 350. Grease an 8x8 square brownie pan.
In a mixing bowl, whisk together the melted butter, sugar, eggs, and vanilla. Mix in the cocoa followed by the flour, salt, and baking powder. Spread batter into the prepared pan.
In the bowl of a stand-mixer fitted with the paddle attachment, beat the cream cheese together with the sugar until smooth. Incorporate the egg yolk and extracts, scraping the sides of the bowl as needed. Add food coloring as desired to reach the color you're wanting (I used about three drops of gel).
Dollop the cream cheese mixture over the brownie batter (you may be tempted to think there is too much cream cheese mixture... but don't worry. When the brownies bake, they puff up and it all evens out nicely). Using a butter knife, swirl the two batters together in an up and down motion. Then, repeat the same motion crosswise until the desired swirling is achieved, being careful not to over swirl.
Bake the brownies for 30-35 minutes or until set, being careful not to overbake. Allow the brownies to cool on a cooling rack for at least 20 minutes before slicing. For clean slices, wipe the knife clean between each slice.