• Preheat the oven to 400°F. Line a 12-cup muffin pan with cupcake liners.
• In a large bowl, whisk together flour, baking powder, cinnamon, salt.
• In the bowl of a stand mixer, cream the butter for about 2 minutes, until smooth and fluffy.
• Add both granulated sugar and light brown sugar, and cream for 3-5 minutes.
• Add the egg and vanilla, and beat together for 1 minute, just until incorporated.
• While the mixer is on low, gradually alternate adding the dry ingredients and the milk, just untl ingredients are incorporated.
• Pour batter into each muffin liner, about ¾ of the way full.
• Bake at 400°F for 5 minutes. Then lower heat to 350°F for 10-12 minutes, until a toothpick inserted into the center of the cupcake comes out clean.

Make the Frosting

• While the cupcakes are baking, start making the frosting by beating the butter in the stand mixer.
• Slowly add the powdered sugar, about 1 cup at a time, beating until incorporated.
• Add the cinnamon, salt, and vanilla, and beat just until incorporated.

Assemble the cupcakes

• Allow the cupcakes to cool completely before frosting them.