01 - Preheat oven to 400°F. Line a baking sheet with parchment paper. Toss pitted, halved cherries with 1 tablespoon sugar and 1 teaspoon vanilla extract. Spread evenly on prepared sheet and roast for 12–15 minutes until juicy and slightly caramelized. Set aside to cool.
02 - Reduce oven temperature to 350°F. Generously butter an 8-inch square baking pan and line with parchment paper, allowing a 2-inch overhang on opposite sides for easy removal.
03 - Set a heatproof bowl over a saucepan of simmering water, ensuring the bowl doesn't touch the water. Add butter and chopped chocolate. Stir constantly until completely melted and smooth. Remove from heat and let cool for 5 minutes.
04 - Whisk granulated sugar and brown sugar into the warm chocolate mixture until fully dissolved. Add eggs one at a time, whisking well after each addition. Stir in vanilla extract and salt.
05 - Sift flour and cocoa powder directly into the batter. Using a spatula, gently fold until just combined. Do not overmix—a few streaks of flour are acceptable.
06 - Reserve approximately 2 tablespoons of roasted cherries for topping. Gently fold the remaining cherries into the batter, being careful not to overmix.
07 - Pour batter into the prepared pan, spreading evenly with an offset spatula. Scatter reserved cherries across the surface. Bake for 25–28 minutes until a toothpick inserted in the center comes out with moist crumbs. The edges should be set but the center slightly soft.
08 - Cool completely in the pan on a wire rack, approximately 2 hours. Lift out using the parchment overhang and cut into 12 squares. For clean cuts, wipe the knife between slices.