Rinse the berries and dry on paper towels. Remove the milk from the refrigerator until it is at room temperature. Separate the whites from the yolks. Prepare a baking dish. Preheat the oven to 180 degrees.
Prepare the dough. Add stevia, coconut, flour and vanilla to a bowl with yolks. Pour in milk and whisk until smooth. Beat the whites in a separate bowl until they become fluffy. Add the protein to the mixture and mix.
Bake a pie. Pour the batter into the pan and spread the blackberries on top. Bake the pie in an oven preheated to 180 degrees for 30 minutes, checking for doneness with a toothpick.
To highlight the sourness of the blackberries, sprinkle the pie with powdered sugar.