Preheat oven to 350 degrees.
Cream the coconut oil and coconut sugar on high in a stand mixer or with an electric beater for two minutes until it's light and fluffy. This really helps the texture if it's beaten well.
Lower the speed to low and add in the eggs one at a time, along with the vanilla until incorporated.
In a separate bowl sift together the flour, salt, and baking powder.
Add the flour into the batter on low speed in three stages. Turn off the mixer as soon as it's incorporated. DON'T OVERMIX!
Add a tsp. of flour to coat the blueberries. This will keep them from falling to the bottom of the muffins.
Mix in the blueberries with a spatula or turn on the mixer and let it go for two to three turns around the pan, them turn off.
If you are using frozen blueberries, the batter will get very cold, that's OK. It will just increase the baking time by a couple of minutes.
Liberally grease a 12 cup muffin pan with coconut oil. Grease the top of the pan as well in case the muffins hit the top of the pan.
Grease your scooper with coconut oil. This will help batter to slide out.
Scoop into 12 muffins.
Bake for 23-28 minutes or until the muffins just spring back to the touch. If using fresh blueberries, check them at 20 minutes.
Let cool for 5-10 minutes before removing from the pan.