Preheat oven to 350 degrees F. Line muffin tins with cupcake liners.
In a bowl mix together flour, baking powder, cinnamon and salt.
In your mixer bowl beat butter and add in sugar, eggs and vanilla extract.
Alternately, add in dry ingredients and milk. Mix just until combined. Do not overmix.
Pour batter into cupcake liners, 2/3 full.
Bake for 18-20 minutes or until a toothpick comes out clean.
Cool and frost.
Frosting
Use an electric hand mixer or stand mixer to make frosting.
In a bowl combine softened butter, powdered sugar, vanilla, cinnamon and milk. Add milk a tablespoon at a time to achieve a good spreading consistency. If needed, add additional milk or powdered sugar.
Use a piping bag to pipe on frosting or use a knife to spread it on when cupcake are completely cool.
Notes
Work with ingredients that are room temperature. They will combine more smoothly.
Always use a liner. It makes removing, frosting and handling the cupcake so much easier. If you don't have liners be sure and spray the muffin tin well.
To make sure my cupcakes are all the same size I always use a scoop and fill the muffin tins 2/3 full.
Allow the snickerdoodle cupcakes to cool for a few minutes in the muffin tin and then remove them to a cooling rack to finish cooling. The heat from the pan will continue to cook them.