Preheat the oven to 180C/350F and grease a muffin tin or 12-count silicone muffin pan and set aside.
In a large mixing bowl, combine all your dry ingredients and set aside. In a separate small bowl, add the rest of your ingredients, except your blueberries, and mix well. Combine the wet and dry ingredients and mix until just combined. Fold in your blueberries and let the batter sit for 5 minutes.
Evenly distribute the muffin batter amongst the muffin tin, about 2/3 of the way full. Bake for 20-25 minutes, or until a skewer comes out clean.
Allow cooling in the pan for 5 minutes, before transferring to a wire rack. Drizzle with the glaze.
For the glaze
Whisk together the keto powdered sugar and lemon juice until thin.
* The lemon extract I used was very strong, and 1 tablespoon was plenty. If you prefer a more pronounced lemon flavor, add some lemon juice.TO STORE: Muffins will keep at room temperature in a sealed container, for up to 5 days. Store them in the refrigerator if you'd like them to keep longer. TO FREEZE: Place muffins in a ziplock bag and store them in the freezer for up to 6 months. If you plan on storing the muffins in the freezer, omit the glaze.