Preheat the oven to 375 degrees F. Spray a standard muffin pan generously with non-stick cooking spray. Set aside.

Wet ingredients: Add butter and granulated sugar to a large mixing bowl or the bowl of a stand mixer. Cream together for about 2 minutes, until smooth and well combined. Add egg. Add vanilla, milk and Greek yogurt and mix until combined.

Dry Ingredients: Stir flour, baking powder, baking soda, cinnamon and salt in a bowl.

Combine dry ingredients with wet, stirring just until combined. Divide batter evenly between prepared muffin cups, filling each about 2/3 full.

Bake at 375 for 15-20 minutes or until a toothpick inserted in the center comes out clean or with just a few moist crumbs. Allow to cool in the muffin tin for a minute or two before removing to a wire cooling rack.

Cinnamon Sugar Topping: While the muffins bake, melt the butter for the topping. In a separate small container, mix together the granulated sugar and cinnamon.

Once muffins are out of the pan, use a pastry brush to brush a thin layer of melted butter over each muffin, then sprinkle generously with cinnamon sugar. (Alternately, dip the muffin tops in melted butter, and then cinnamon sugar).