Preheat oven to 350° F. Position oven rack to the lower third of the oven. Line a six cup muffin tin with paper liners.
Measure the coconut flour, sweetener, baking powder, salt, cinnamon and xanthan gum together in a small bowl and whisk to combine and break-up any lumps. Set aside.
In a medium bowl, cream the butter, cream cheese and vanilla together until light and fluffy. Add 1 egg and beat into the butter mixture until the mixture is light and fluffy (it may break or separate, it’s okay).
Add 1/3 of the dry ingredients and mix until completely incorporated, making sure to keep that light, fluffy texture. (Keep in mind that we want a light and fluffy – almost mousse-like texture throughout this process.)
Add another egg and beat until fully combined and the batter is fluffy. Add half of the remaining dry ingredients, beating again. Add the last egg, beating until fully incorporated, followed by the last of the dry ingredients.
Finish by adding the heavy cream, once again, beating until the batter is thick, but still light and fluffy. Fold in the blueberries.
Spoon the thick batter into a plastic zip-loc bag and snip off a corner, producing about a 3/4 inch hole. Place the snipped corner into a muffin liner and squeeze the batter into a fat, rounded mound, filling the muffin liner about 3/4 full. Repeat for each muffin liner, adding any remaining batter to those that need a little more. Knock down any peaks with your finger. Evenly sprinkle the tops of the muffins with the 2 tbsp of sweetener to help prevent burning and to give the muffins a nice look.
Place the muffins into the oven. Turn the oven up to 400° degrees for 5 minutes. Then, turn the oven back to 350° and bake the blueberry muffins for about 20-25 minutes more. They’re ready when they feel firm when lightly pressed with a finger, but still sound a little moist.
Remove from the oven and let cool five minutes before gently removing from the pan and placing on a cooling rack.