Preheat your oven to 350°F (175°C) and prepare an 8x8-inch baking pan by greasing it or lining it with parchment paper.

For the brownie base, whisk together the melted unsalted butter, granulated sugar, eggs, and vanilla extract until smooth. Sift in the cocoa powder, all-purpose flour, salt, and baking powder. Gently stir just until combined to maintain a fudgy texture. Spread about two-thirds of this batter evenly in the prepared pan, reserving the remaining batter for later.

For the cheesecake layer, beat the softened cream cheese with granulated sugar until light and fluffy. Mix in the egg and vanilla extract until smooth, then pour this mixture over the brownie base in the pan.

Dollop the remaining brownie batter on top of the cheesecake layer and swirl it gently with a knife or toothpick to create an attractive marbled effect.

For the cherry topping, combine the fresh cherries, cornstarch (dissolved in water), sugar, and lemon juice in a small saucepan over medium heat. Cook until the mixture thickens into a glossy sauce, then spoon it evenly over the layered brownie and cheesecake.

Bake the assembled dessert for 35-40 minutes, or until the center just barely jiggles when the pan is gently shaken. Be careful not to overbake so the brownie remains fudgy and the cheesecake creamy.

Allow the baked brownie to cool completely at room temperature, then refrigerate for at least 2 hours to help set all the layers.

When ready to serve, dip a sharp knife in hot water between cuts to produce clean, perfect slices.