Preheat the oven to 350F.
Make the filling first. Mix the blueberries, lemon juice, zest and sweetener together in a small bowl. Place to one side.
Make the dough: Add the mozzarella and cream cheese to a heatproof glass large bowl. Heat in microwave for 60 seconds, stir and then heat for further 30 seconds until fully melted. Mix well with a spatula.
Add the almond flour, egg, sweetener and optional vanilla. Mix well until combined. Use your hands to kneed into a ball. Wrap in plastic wrap and place in the fridge to chill for 30 minutes.
Split the dough in two. Using a rolling pin, roll one piece of dough out between two sheets of parchment paper or a silicone mat and a sheet of parchment paper, about 3mm thick.
Use a 7.5 inch pan lid to score a circle and cut round with a knife. Repeat with the second piece of dough and re-roll the scraps to make the third circle. You should have 3 circles on 3 pieces of parchment paper and place onto a baking tray pan. If you don’t quite get enough for a circle for the third one it doesn’t matter as you can just fold it up following the steps below.
Place the circles of dough on the parchment back on baking pan, back in the fridge for about 30 minutes. Once chilled, loosen the circles from the parchment using a palate knife and divide the blueberry mix between the circles, placing them in the center.
Fold the outer edges of the dough over the blueberries sealing in the middle by pressing together and turn over using a palate knife so the seal is on the bottom of the pan. Cut two small steam holes in the top with a sharp knife. Not too big or the contents will flow out! Sprinkle with 1 teaspoon of sweetener.
Bake for 25 minutes or until golden brown on top. Allow to cool a little before serving with ice cream, frozen yogurt, whipped cream or coconut cream.