Preheat the oven to 350°F.
Prepare a baking sheet with parchment paper or a silicone mat.
In a bowl, combine the dry ingredients: almond flour, sweetener, coconut flour, baking powder, lemon zest and salt.
Grate the cold butter using a boxed grater (like you’d grate cheese) and combine it with the dry ingredients. Mix with two butter knives (using a slicing motion) or a pastry blender until the texture is like coarse sand.
Mix in the heavy cream and then add the lemon juice.
Fold in the loosely chopped blackberries.
Transfer the dough (it will look crumbly) to your prepared baking sheet and gently work the dough into a loose square. Cut the dough into 9 pieces and gently separate them on the parchment.
Brush the tops with heavy cream.
Bake at 350°F for 16-18 minutes (or until the scones are golden-brown).
While the scones are baking, mix the powdered sweetener and lemon juice in a small bowl to make glaze.
Once scones are slightly cooled (10 minutes), drizzle glaze on the scones using a spoon.
Allow the scones to completely cool on the baking sheet (they'll fall apart if you try to transfer them).