Preheat your oven to 375°F (190°C). Line a 12-cup muffin tin with paper liners or lightly coat with cooking spray. This ensures your muffins release easily and bake evenly. Pro tip: Pro tip: I like to spray the top of the muffin tin as well, as this helps create those beautiful domed tops!

In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside. This combination ensures your muffins will rise properly without any metallic aftertaste. Pro tip: Whisking the dry ingredients prevents lumps and distributes the leavening agents evenly throughout the batter.

In a large bowl, beat the softened butter and sugar together using an electric mixer (or a wooden spoon if mixing by hand) for 2-3 minutes until light and fluffy. This should look pale and slightly increased in volume. Pro tip: Room temperature butter is key! Cold butter won't cream properly, and melted butter will make dense muffins. Leave it out for 30 minutes if needed.

Add the eggs one at a time to the butter mixture, beating well after each addition. Then add the sour cream, lemon zest, lemon juice, and vanilla extract. Mix until just combined and the batter looks smooth. Pro tip: The lemon zest and juice should be added now for maximum flavor distribution. Don't overmix at this stage—just combine until no streaks of sour cream remain.

Gently fold the dry ingredients into the wet ingredients using a spatula or wooden spoon. Mix only until just combined—a few small lumps are perfectly fine! Overmixing develops gluten and results in tough, dense muffins. Pro tip: The key to tender, moist blueberry muffins is a delicate hand when combining the wet and dry ingredients. Stop as soon as you don't see streaks of dry flour.

Gently fold in the blueberries, being careful not to crush them. If using frozen blueberries, do not thaw them first—this prevents them from bleeding into the batter and keeps them intact. Pro tip: Toss frozen blueberries lightly in a tablespoon of flour before folding them in. This helps them stay suspended throughout the muffin instead of sinking to the bottom.

Divide the batter evenly among the muffin cups, filling each about two-thirds full. Bake for 20-25 minutes, or until a toothpick inserted into a muffin (avoiding a blueberry) comes out clean or with just a few moist crumbs. Pro tip: The tops should be golden brown and spring back lightly when touched. Don't overbake, as this will dry them out. Start checking at the 20-minute mark.

Let the muffins cool in the tin for 5-10 minutes, then carefully remove and place on a wire rack to cool completely. Once cooled, prepare the glaze by whisking together the powdered sugar, lemon juice, and lemon zest until smooth. Drizzle over the cooled muffins. Pro tip: The glaze should have a pourable but thick consistency. Add lemon juice one tablespoon at a time until you reach the right consistency. A little drizzle goes a long way!