Preheat your oven to 375 degrees F. Coat a mini muffin tin with non-stick cooking spray.
Stir the flour, baking powder, and salt together in a medium bowl. Set aside.
Beat together the sugar and melted butter in a large bowl. Stir in the milk and vanilla. Add the dry ingredients and mix until just combined.
Use a small cookie scoop or spoon to portion the muffin batter into the prepared muffin tin. The cup should be about 1/2 to 3/4 full. (use all the batter)
Bake for 15 to 20 minutes, or until the top of the muffins are lightly golden and a toothpick inserted in the center comes out clean.
Transfer the muffins to a cooling rack and allow them to until cool enough to touch.
Coating
Place the melted butter in a small bowl. Then combine sugar and cinnamon in another small bowl.
Dip each muffin in the melted butter, and then roll in the cinnamon sugar until completely coated. Return the muffins to the wire rack to cool. Serve slightly warm or at room temperature.