Line 24 muffin cups with paper baking cups and set aside.
In a large mixing bowl, beat butter on medium for 30 seconds. Gradually add sugar a ¼ cup at a time, beating until well combined.
Add eggs, one at a time, beating after each. Beat in vanilla extract. Add flour and milk alternately, beating on low after each addition until well combined.
Add baking powder, salt and cinnamon and mix well.
Spoon batter into prepared cups, filling about ½ full. Combine 3 tablespoons sugar and 2 teaspoons cinnamon. Sprinkle half of the cinnamon-sugar mixture over the batter making sure the batter is completely covered.
Bake approximately 20 minutes or until a toothpick comes out clean. Cool cupcakes in pan for 5 minutes. Remove cupcakes from pans and cool on wire rack.
MAKE BUTTERCREAM FROSTING
In a very large mixing bowl beat butter on medium until smooth.
Gradually add 2 cups of the powdered sugar, beating well. Slowly beat in the ¼ cup milk and vanilla extract. Gradually beat in remaining powdered sugar and cinnamon until smooth.
Spoon frosting into a large pastry bag fitted with a large star tip. Pipe frosting on cupcake. Sprinkle with the remaining cinnamon-sugar mixture.