Preheat your oven to 350°F (175°C) and line a muffin tin with paper liners.

In a bowl, cream together the softened butter, granulated sugar, and brown sugar until fluffy.

Beat in the eggs one at a time, followed by the vanilla extract.

In another bowl, combine the flour, baking powder, baking soda, salt, and cinnamon.

Gradually add the dry ingredients to the wet mixture, alternating with sour cream.

Mix until just combined; do not overmix.

Prepare the streusel topping by combining ½ cup flour, ¼ cup brown sugar, and ¼ cup butter with cinnamon.

Fill the muffin cups about 2/3 full with batter.

Sprinkle the streusel topping generously over each muffin.

Bake for 20-25 minutes or until a toothpick comes out clean.