In the blender or food processor, add the oats first and then the rest of the ingredients except the blueberries. Blend until smooth. Stir in half the blueberries.
Pour batter evenly into a greased or lined 12-cup muffin pan (see note). Top with remaining blueberries.
Bake for 25-30 minutes, until inserted toothpick comes out clean.
Cool completely (wait at least 10 minutes) before taking them out of the pan.
Notes
I recommend using fresh if possible. If using frozen, add them directly to the batter without thawing them. You can also toss them with a tablespoon or so of flour.
No kefir? Plain Greek yogurt (use the same amount or a bit less) will be the best alternative.
No dairy? Any plant-based alternative will work. Look for plain and unsweetened though as many contain added sugars. Several readers have told me that coconut yogurt worked really well!
No applesauce? You can puree fresh apples or pears. Can also try using mashed banana or sweet potatoes (add a little bit of water so it's similar in consistency to applesauce).
No banana? Use 3 medjool dates (soaked in warm water for at least 30 minutes to make them easier to blend. Will also result in a smoother consistency.
I like to use a silicone baking pan as there's no need to grease and is easy to clean!
If you find that the muffins are too moist, put them in the fridge to help firm up.
Store in an airtight container for 3-5 days in the fridge or in the freezer for up to 3 months.