Preheat the oven to 400 degrees F. Line a muffin tin with paper liners or spray a silicone muffin pan.
In a large bowl, combine flour, oats, sugar, baking powder and salt. Combine well. Add in melted coconut oil and mix well.
In a small bowl, whisk egg, milk, sour cream, lemon zest and vanilla until blended. Fold egg mixture into dry mixture and combine until moistened. Carefully fold in blueberries (and some chocolate if you'd like!). Let the batter set for 5 minutes.
Scoop batter into muffin cups about ¾ full. Bake 20-22 minutes until golden on top and a toothpick inserted comes out clean. Remove muffins from a metal pan right away and transfer to a cooling rack to cool. If using a silicone pan, let cool 5 minutes before transferring to a cooling rack.
Tip: Leaving the muffins in the pan will make them continue to cook and may dry them out. To avoid this take them right out from a metal one.