"This brownie cookie bar recipe kind of combines brownies and cookies, except that the brownies are square and thin enough to be considered a cookie! When fully cooked, sprinkle powdered sugar over top, cut into squares, and they're ready to eat! If you scale down the recipe, you may want to use a smaller pan because these are meant to be thin. Trust me, they go fast!"
Preheat the oven to 350 degrees F (175 degrees C). Grease a 9x13-inch baking pan.
Combine sugar, butter, eggs, and vanilla extract in a bowl. Beat in flour, cocoa powder, salt, baking powder, cinnamon, and allspice. Spread batter into the prepared pan; it will just barely reach the corners.
Bake in the preheated oven until top is dry and edges have started to pull away from the sides of the pan, 20 to 25 minutes. Sprinkle confectioners' sugar on top and cut into squares.