Preheat oven to 350°F. Grease 8×8 baking pan or line with parchment paper.
In large bowl, combine the butter, sweetener, cocoa, vanilla extract, and salt until well combined.
Whisk in the eggs then fold in the flours.
Reserve about ¼ cup of batter. Spread remaining batter into prepared pan.
Beat together the cream cheese, sweetener, vanilla, and egg yolk until well blended.
Spread cream cheese mixture evenly over brownie layer.
Drop reserved brownie batter over cheesecake layer.
Swirl in with a knife.
Bake for about 30 minutes then transfer to a rack to cool.
Customize with add-ins. By adding your favorite toppings or mix-ins, you can customize them to your own taste. Try mixing in chocolate chips to the batter or sprinkling them on top of the cheesecake layer before baking.Thin the reserved batter. If the brownie batter for the swirl is too thick, you can thin it with a little hot water or almond milk. A thinner batter is easier to swirl in.Do not over-swirl. Make big swirls to cover the entire top of the brownies being careful not to overdo it for best results.Add espresso powder. For a more intense chocolate flavor, you can add in a teaspoon or more of instant espresso powder.Use a brownie mix. To make this recipe even easier, you can substitute your favorite brownie mix for the homemade brownie batter.