Heat the oven to 350 degrees F.
Generously grease the bottom and all sides of the muffin pan with butter.
In a large mixing bowl, add butter and sugar. Beat until light and fluffy.
Next add flour, sour cream, eggs, baking soda, baking powder, and vanilla extract. Beat on a low speed until blended. Then beat for another 3 minutes.
Add the batter to the muffin pan only filling the space halfway for each muffin. Set aside for a moment.
In a separate small bowl, mix the cinnamon and sugar. Then generously top the batter with half of the cinnamon and sugar mixture.
Next, add another layer of batter for each muffin.
Lastly, top the batter with the remaining cinnamon and sugar mixture. Bake until the inside of each muffin is still slightly moist (about 27 minutes; use a toothpick to test the middle of the muffin, if the toothpick comes out with a small amount of moist cake on it then remove it from the oven to cool). These muffins are best when baked so that the middle of the muffin is as moist as possible otherwise they tend to dry out.
Let the muffins cool; when the muffins are cool enough to handle, carefully remove them from the muffin pan.
Serve with plain or with softened butter.