Preheat oven to 375°C/190°F degrees. Butter 12 muffin cups or line them with liner papers.
In a large bowl, combine sifted flour, baking powder, baking soda and salt. Set aside.
In a large mixing bowl, add sugar and lemon zest and mix for 15 seconds. Then whisk in melted butter, oil, egg, sour cream, whole milk, lemon juice and vanilla extract until just combined. You can do this by hand with a whisk or with a hand mixer.
Pour the wet ingredients over the dry ingredients and carefully stir with a wooden spoon or a rubber spatula until the two mixtures are just combined. The batter will be thick and a little lumpy. Don't overmix. Carefully fold in the blueberries.
Divide the batter evenly between the muffin cups (filling 3/4 full). Add streusel if desired (read my post). Bake for 18-23 minutes or until a toothpick inserted into the center of the muffin comes out clean. Cool for 10 minutes and then move to a wire rack to cool completely.
Once muffins are cooled, add glaze if desired. Muffins are best the same day they are made but can be stored in an airtight container in the fridge for up to 3 days, or they can be frozen for up to 2 months.