Snickerdoodle Muffins

Name: Snickerdoodle Muffins
Prep time: 25 min
Cook time: 10 min
Total time: 35 min
Cuisine: American
Ingredients: 6 tablespoons butter, (at room temperature); 1/2 cup granulated white sugar; 1 large egg; 1/2 cup milk; 1 teaspoon vanilla extract; 1½ cups all purpose flour; 1½ teaspoons baking powder; 3/4 teaspoon cream of tartar; 1/4 teaspoon salt; 1/2 teaspoon cinnamon; 1/3 cup granulated white sugar; 1 teaspoon cinnamon; 2 tablespoons butter, (melted)