Although this bar is as rich and moist as cake, you don't need a fork to enjoy it. The kirsch-spiked filling will appeal to grown-up tastes; for kids, simply omit the liqueur.
Preheat oven to 325 degrees. Coat a 9-inch square baking pan with cooking spray; line with parchment paper, allowing a 2-inch overhang. Coat with cooking spray.
Bring cherries, 2 tablespoons butter, 1/4 cup granulated sugar, and the water to a simmer in a saucepan over medium heat. Simmer, stirring occasionally, until almost all liquid has been absorbed, about 15 minutes. Remove from heat; stir in 1/4 cup granulated sugar. Let cool, stirring occasionally, until sugar has dissolved.
Whisk together cocoa powder, salt, brown sugar, toasted coconut, and 2 cups flour in a bowl. Blend in remaining 2 1/4 sticks butter with a pastry blender or your fingertips until mixture resembles coarse meal; press 3 lightly packed cups cocoa mixture into prepared pan. Bake until just set, about 20 minutes.
Put egg, remaining 1/2 cup granulated sugar, and the kirsch, if using, in the bowl of an electric mixer fitted with the whisk attachment; mix on medium-high speed until pale, about 4 minutes. Fold in cherry mixture and remaining 7 1/2 teaspoons flour; stir in chocolate. Spread mixture evenly over crust; sprinkle with remaining cocoa mixture.
Bake until a cake tester inserted into center comes out clean, about 50 minutes. Let cool completely on a wire rack. Run a knife around sides; lift out of pan. Cut into squares. Bars can be stored in an airtight container at room temperature up to 5 days.