Mix almond flour, coconut flour, baking powder and salt in small bowl. Set aside. In separate bowl, whisk eggs, butter, water, erythritol, stevia and lemon extract. Mix dry ingredients into wet ingredients and stir until well combined. Fold in blueberries.
Spoon batter equally into 6 muffin cups. Bake for 20-25 minutes or until lightly brown. Cool in pan 5-10 minutes then remove from pan and cool muffins on rack.
1 teaspoons vanilla extract can be added for a to enhance and sweeten the taste.The erythritol and stevia can be substituted with 1/3 cup honey or coconut sugar for those not following low carb.Net carbs per muffin: 4 g