Preheat the oven to 400º.
Melt your butter in the microwave or on the stove top. Let cool for a few minutes.
Line your muffin tin with baking liners or spray with cooking spray. Set aside.
In a large mixing bowl, whisk together your melted butter and sugar.
Add in your room temperature eggs (if your eggs are still cold you can run them under warm water for a minute or two) and whisk to combine.
Add in your milk and vanilla extract and mix until the wet ingredients are fully combined.
Next, add in your dry ingredients - ground cinnamon, salt, baking powder, and all-purpose flour. Switch to a rubber spoon or spatula and stir to combine. Be sure not to overmix.
Add blueberries and flour to a separate bowl and gently stir, ensuring the blueberries are coated in the flour. This helps to ensure the blueberries don’t sink to the bottom of the muffins while baking.
Add the flour-coated blueberries to the muffin batter and fold in gently.
Fill each muffin space between 1/2 and 3/4 full, approximately 2/3 full. Bake for 20 minutes or until a toothpick inserted comes out clean.
Allow to cool 5-10 minutes before removing from pan.
Enjoy!