Ingredients:

1 cup unsalted butter, softened
1 cup sugar
2 teaspoons vanilla
2 eggs
¾ teaspoon baking soda
¾ teaspoon baking powder
¾ teaspoon cream of tartar
1/2 teaspoon ground cinnamon
1/2 teaspoon ground nutmeg
1 1/4 cups sour cream
2 1/4 cups flour (I used Self-Raising, but I think they used Plain)
1/2 cup sugar + 1 tablespoon cinnamon mixed together for rolling

Directions

Preheat oven to 350 degrees.

Grease muffin pans, or line with baking cups.

In a large bowl, cream the butter and sugar until soft, about 3 to 5 minutes.

Stir in vanilla, then add the eggs one at a time and mix until each is incorporated.

In a separate bowl, mix together the flour, baking soda, baking powder, cream of tartar, cinnamon and nutmeg.

Add the flour mixture to the sugar/butter mixture, alternating with the sour cream. Start with the flour and end with the flour, scraping down the bowl occasionally.

Using an ice cream scoop or large spoon, scoop out muffin batter and drop into a shallow bowl filled with the cinnamon sugar mixture. Roll the muffin around in the mixture until it is covered completely in cinnamon sugar.   This isn’t as difficult as it sounds.

Place in prepared pan.  Continue scooping dough and rolling in cinnamon/sugar until all batter is used.

Bake them for 20-25 minutes, or until golden brown.

Source: http://letsdishrecipes.blogspot.com/2010/05/snickerdoodle-muffins.html