Preheat your oven to 350 degrees. Line a 12-cup muffin tin with cupcake liners.
In a mixing bowl, cream together the butter and sugar and then add the eggs one at a time.
Sift together the flour, baking powder, baking soda, and salt and then stir them gently into the butter mixture. Mix until just combined, and then add in the sour cream, vanilla, lemon juice, and lemon zest. Do not overmix.
Toss the blueberries with a tablespoon of flour and then gently stir them into the batter.
Divide the batter between the muffin cups. Sprinkle the sugar over the top of each muffin.
Bake for twenty minutes, or until a toothpick inserted into the center come out free of batter.
Let the muffins cool in the pan on a wire rack for five minutes, and then out of the pan for 10 minutes.