Preheat oven to 350 F, and grease or oil 12 cup muffin pan (could also line with paper muffin cups, and could oil those a little too).
In large mixing bowl, beat with an electric hand mixer or stand mixer all the cheese Danish filling ingredients: cream cheese, optional sour cream, lemon juice, vanilla extract, sweetener of choice, and egg yolk. Set aside.
In a separate large mixing bowl sift the coconut flour, and add: sea salt, & low carb sweetener Set aside.
In separate, large mixing bowl combine: eggs, milk of choice, melted butter or coconut oil, vanilla extract, lemon juice, lemon zest.
Combine: Egg milk liquid mixture with coconut flour dry mixture. Stir together thoroughly.
Add baking powder and apple cider vinegar. Mix together well.
Add blueberries to the coconut flour batter and fold in.
Fill muffin pan cups 2/3 full with coconut flour batter.
Use a spoon to make an indentation in the center of each muffin (as seen in photo above).
Use a spoon to fill the hollow center of each muffin with the cheese Danish mixture (as seen in photo above).
Bake in oven for 25 to 30 minutes or until center is set and tops are golden (check at 25 minutes as all ovens vary).
Cool completely before removing papers and serving. Can refrigerate then serve, and all leftovers should be stored in the fridge.
NUTRITIONAL DATA FOR LOW CARB VERSION (using Swerve ): Serving size: 1 muffin out of 12, Cal: 111, Fat: 9 g, Carbs: 5.5g / Net Carbs:3.5 g, Fiber: 2 g, Protein: 3 g, Sugar: 1 g*all nutritional data are estimates based on the products I used*