Preheat oven to 375 degrees F. Line a muffin tin with 9 paper liners, or spray with non-stick cooking spray.
Melt butter in a large bowl (I find that 45 seconds in a microwave does the trick). Add in granulated sugar, brown sugar, lemon zest, and sour cream, and use a whisk to combine ingredients.
Whisk in egg and vanilla extract.
Next, add in baking powder, baking soda, salt, and cinnamon, and whisk together.
Add the flour and blueberries, and use a rubber spatula to gently fold them into the muffin batter just until combined. Don't overmix! There should still be a little bit of flour visible at this point, and the batter will be very thick.
Using a large cookie scoop or ice cream scoop, divide the muffin batter between the prepared muffin cups, filling them all the way to the top.
Sprinkle the tops of each muffin with ½ teaspoon granulated sugar, and bake for 25-30 minutes, until the tops are golden and a toothpick inserted into the center comes out clean.
Let the muffins cool for 5 minutes, then transfer them to a cooling rack to cool completely.