Preheat oven to 325 degress F. Line baking sheets with waxed paper. Beat egg whites in a glass or metal bowl until foamy. Gradually add sugar, continuing to beat until stiff peaks form. Lift your beater or whisk straight up: the egg whites will form sharp peaks. Beat cocoa powder, vanilla extract, and salt into egg white mixture until incorporated; fold in coconut. Drop spoonfuls of coconut mixture onto the prepared baking sheets. Bake in the preheated oven until coconut starts to brown, about 20 minutes. Press a cherry half into the top of each macaroon; transfer cookies to a cooling rack.