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