In a medium bowl; whisk together the melted butter and 1 cup of sugar.
1/2 cup (114g) unsalted butter, 1 cup (200g) granulated sugar
Then whisk in the eggs, milk, lemon zest, lemon juice, and vanilla.
2 large eggs, 3/4 cup (188ml) milk, zest of 1 lemon, 2 Tbsp lemon juice, 1 tsp vanilla extract
Add the wet ingredients to the dry ingredients, and gently stir using a rubber spatula until just combined. Fold in the blueberries.
2 cups blueberries
Divide the batter into the 12 muffin cups. Generously sprinkle the remaining sugar over the tops.
1/4 cup (50g) granulated sugar
Bake for 20-22 minutes or until a toothpick inserted into the center comes out clean.
Notes
Leftovers can be placed in an airtight container and store at room temperature for up to 3 days or in the fridge for up to 5 days. Warm up the refrigerated muffins in the microwave for 15-30 seconds if desired.To freeze - Skip the extra sugar on top before baking. Let the muffins cool completely and place them in a freezer-friendly container or ziplock bag. Store in the freezer for up to 2 months. Thaw overnight in the fridge. Generously sprinkle with sugar on top and reheat in the oven at 350F for 5-10 minutes until warmed up and crisp on top.