01 - Preheat oven to 400°F. Line a baking sheet with parchment paper.
02 - Toss pitted, halved cherries with 1 tbsp sugar and 1 tsp vanilla. Spread on prepared baking sheet. Roast for 12–15 minutes until juicy and slightly caramelized. Cool completely.
03 - Reduce oven temperature to 350°F. Grease an 8-inch square baking pan with butter and line with parchment paper, leaving overhang for easy removal.
04 - Set a heatproof bowl over a saucepan of simmering water. Add butter and chopped chocolate. Stir until completely melted and smooth. Remove from heat and cool slightly.
05 - Whisk granulated and brown sugars into chocolate mixture until combined. Add eggs one at a time, whisking well after each addition. Stir in vanilla and salt.
06 - Sift flour and cocoa powder into the batter. Gently fold with a spatula until just combined. Do not overmix.
07 - Fold in most of the roasted cherries, reserving a few pieces for the topping.
08 - Pour batter into prepared pan. Smooth top with spatula. Scatter reserved cherries over surface. Bake for 25–28 minutes until a toothpick inserted in center comes out with moist crumbs. Avoid overbaking.
09 - Cool completely in pan. Lift out using parchment overhang. Cut into 12 squares.