Place butter in a roughly 8×8 casserole pan, pie pan or cast iron skillet and place in the oven to let the butter melt.
In a large mixing bowl, whisk together flour, milk, eggs and cinnamon or vanilla.
Remove casserole pan from oven and swirl butter around to coat all sides of pan. Pour ingredients into the pan and return to the oven. Let bake approximately 30 minutes until the edges are crispy and the top has hints of golden brown.
Serve with your favorite toppings, such as applesauce, fresh fruit, jam, nutella, maple syrup or peanut butter.