Add the blueberries to a small, separate bowl and sprinkle a 1 tbsp of flour over them. Stir to coat, then set aside. (This helps the berries not sink to the bottom of the muffins while baking.
In a large bowl, whisk together the melted butter, granulated white sugar, eggs, sour cream, milk and vanilla extract.
1/2 cup (112 g) unsalted butter, melted, 1 cup (200 g) granulated white sugar, 2 eggs, at room temperature, 1 tsp vanilla extract, 1/2 cup (122 g) sour cream, 1/2 cup (120 ml) whole milk, at room temperature
Add the dry ingredients to the wet ingredients and whisk just until combined.
Add in the blueberries and gently fold them into the batter with a rubber spatula.
Cover the batter with plastic wrap and let it rest at room temperature for 1 hour. (This helps the muffins to be extra fluffy.)
Preheat the oven to 350 degrees.
After one hour scoop the batter into the prepared muffin pan. Be careful not to mix the batter around after it has rested, just scoop it into each liner. Add extra blueberries on top of each muffin and sprinkle with turbinado sugar.