Preheat oven to 400°F. Whisk together milk, flour and salt until smooth. Add slightly beaten eggs and beat well. Melt the butter in a pie plate in the hot oven. When the butter has melted, remove from the oven and tilt to coat the bottom and sides of the pie plate. Quickly pour in egg mixture and sprinkle with cinnamon.
Bake for 15 minutes. Remove from the oven and serve while still hot. Drizzle with the topping of your choice or sprinkle with powdered sugar.