Preheat oven to 425ºF. Place the butter in a 9x9-inch square glass baking dish and put in the oven to melt. Keep an eye on it so it doesn't burn!Meanwhile, in a medium bowl, whisk together the dry ingredients.Measure out the milk and maple syrup in a 2-cup liquid measuring cup. Add eggs and whisk well with a fork. Gradually add melted butter to the milk mixture, making sure to leave 2 tablespoons in the bottom of the baking dish.Add the wet ingredients to the dry ingredients and whisk just until the flour is all moistened. Scrape the batter into the buttered baking dish and spread it out with a spatula. Bake in preheated oven for 20–25 minutes, or until the edges are beautifully golden brown and a toothpick inserted in the center comes out clean.Serve hot with butter and maple syrup.