Preheat oven to 350 °F (175 °C). Line a 9×9‑inch baking pan with parchment paper, leaving overhang.

In a medium bowl, whisk melted butter and sugar until smooth. Add eggs one at a time, then vanilla, and whisk until glossy.

Sift in flour, cocoa, and salt; gently stir until just combined.

In a separate bowl, beat cream cheese, sugar, egg yolk, and vanilla until silky smooth.

Pour half the brownie batter into the prepared pan, spreading evenly. Spoon cheesecake mixture over brownie layer, then dollop cherry pie filling on top. Swirl gently with a knife to create a marbled effect.

Carefully spoon remaining brownie batter over the top and swirl again lightly, adding chocolate chips if using.

Bake for 35–40 minutes, until the edges are set and the center is slightly gooey. A toothpick will come out with moist crumbs.

Cool fully in the pan on a wire rack. Use the parchment overhang to lift brownies out; slice into 16 squares.