Step 1

Preheat the oven to 350ºF. Line muffin cups with muffin liners. (Do not use cooking spray.)

Step 2

In a large bowl whisk together flour, baking powder, baking soda, cream of tarter, nutmeg, and salt; set aside.

Step 3

In the bowl of a stand mixer fitted with the paddle attachment, cream the butter and sugar until light and fluffy, about 3 minutes. Add eggs, one at a time, beating well after each addition. Beat in vanilla extract. Beat in half of the dry ingredients. Beat in the sour cream and buttermilk. Beat in remaining dry ingredients until just incorporated (batter will be soft).

Step 4

To make the topping, in a small bowl, combine the sugar and cinnamon.

Step 5

Using an ice cream or large cookie scooper, drop the scoop of batter into the bowl with the sugar and cinnamon. Sprinkle the dough with the mixture and roll it around until it is covered completely in cinnamon sugar. Place the ball into the muffin liner. Repeat with remaining batter. Sprinkle the leftover cinnamon sugar onto the tops the muffins.

Step 6

Bake until muffin tops are golden brown, 18 to 22 minutes, or until toothpick inserted into the center of a muffin comes out with a few moist crumbs attached. Set on wire rack to cool slightly, about 5 minutes. Remove muffins from tin and serve warm.