Preheat oven tp 400 degrees.
Add butter to skillet and put in oven to melt while you mix other ingredients.
Mix flour, sugar, cinnamon, salt, and baking powder in a large bowl. Add milk in slowly and mix it all together.
Pull skillet with melted butter from the oven, and pour in the batter. The melted butter will gather around the edges. Take a basting brush and spread the butter over the top of the batter.
Once the butter is spread over the top of the batter, sprinkle the teaspoon of sugar and the teaspoon of cinnamon over the top of the batter.
Pop back into the oven for 20-25 min. You want the edges to start turning brown. Check the middle to make sure it is done.
While it's cooling, add butter, powdered sugar and vanilla to a bowl. Start by adding 1 tablespoon of HOT water at a time to the mixture. Do not use more than 3 tablespoons total of water. Mix well.
Once the coffee cake has cooled some, pour the icing over it. It will form into a nice glaze over the top the coffee cake.
Serve and Enjoy!