Instructions:

1. 1. Preheat Oven and Grease Muffin Pan: Preheat oven to 375°F (190°C). Grease a muffin pan with non-stick cooking spray.
   2. Cream Butter and Sugar: In a large bowl, cream together butter and sugar until smooth.

1. 1. Add Wet Ingredients: Add egg, vanilla, milk, and sour cream. Mix until combined.

1. Add Dry Ingredients: Add flour, baking powder, baking soda, cinnamon, and salt. Fold in until just combined.
2. Fill Muffin Pan: Spoon batter into greased muffin pan. Insert a toothpick into the center of each muffin.
3. Bake: Bake for 25 minutes, or until a toothpick inserted into the center comes out clean.
4. Cool: Let muffins cool in the pan for 1-2 minutes, then transfer to a wire rack.
5. Make the Topping: Melt butter and mix with granulated sugar and cinnamon.
6. Add Topping: Brush melted butter onto cooled muffins and sprinkle with cinnamon-sugar mixture.

Serve warm and enjoy!