Preheat the oven to 350 degrees Fahrenheit and spray a standard muffin tin with a non-stick cooking spray.
Cream together the butter, granulated sugar and brown sugar with a hand held mixer or stand up mixer until smooth and combined (2-3 minutes).
Then mix in the eggs, milk, sour cream and vanilla extract until combined.
Stir in the flour, cinnamon, baking powder, baking soda and salt by hand with a wooden spoon or spatula until just combined. Be careful not to over mix.
Scoop the batter into the prepared muffin tin until each one is approximately 2/3 of the way full.
Bake for 18-20 minutes until a toothpick inserted into the center of the muffins comes out clean.
Allow the muffins to sit in the tin for 5 minutes, then carefully remove the muffins and place them on a wire rack to cool.
Melt the butter for the topping. In a separate bowl, stir together the sugar and cinnamon for the topping.
Once the muffins have cooled for a few minutes, brush the melted butter on the outside of each muffin and sprinkle the cinnamon and sugar mixture on top. Make sure to get all around the muffins!
Once the muffins have been coated, they are ready to serve and enjoy!
Notes
I don’t use cupcake liners for this recipe as I want to coat the cinnamon and sugar mixture on all sides of the muffins. Make sure to spray the tin generously with the non-stick spray so that they are easy to remove. These muffins are best served fresh or within a few days but you can store any leftovers in an airtight container at room temperature for up to 5 days. They are best microwaved for 15-20 seconds before enjoying the leftovers.