1/2 stick butter, melted
1/4 cup sugar
½ tsp cinnamon
Position oven rack in the middle position and preheat oven to 400 degrees F. Line a standard muffin pan with paper cups sprayed with non-stick spray.
Whisk flour, baking powder, baking soda and salt in a large bowl. In a separate bowl, whisk together eggs, sour cream/yogurt, sugar, oil, and vanilla. Add flour mixture and mix with light strokes until the dry ingredients are just moistened. Don’t overmix; batter will be slightly lumpy.
Divide batter among the muffin cups and bake until a toothpick inserted in one or two of the muffins come out clean, 12-15 minutes.
While the muffins are baking, melt 1/2 stick butter and place in a bowl just large enough to hold a muffin. Combine 1/2 cup sugar and 1 tsp. cinnamon in a small, shallow bowl. As soon as the muffins are done, dip them one at a time in the melted butter and then roll in the sugar mixture. Set on a rack to cool.
Yields 12 standard muffins.