To make the dough: Add all ingredients into a large bowl and mix with a wooden spoon until the dough comes together.
If the dough it too wet, add a bit more almond flour; if it's too dry, add a few tablespoons of water and knead until it's no longer clumpy
Wrap the dough in plastic wrap and stick in the fridge for 15 minutes.
Meanwhile, make the filling: In a medium-sized saucepan, add the blackberries, sugar (or Swerve, if using), lemon juice (if using), salt, and vanilla extract.
Cook on medium heat until the ingredients come together and the blackberries have softened and released their juices and the mixture thickens, about 10 minutes. Be careful not to overcook and burn the filling.
Let the filling cool for 10 minutes, then add to a bowl with the softened cream cheese and stir until fully mixed but you still see some "swirls" - you don't want the mixture to be TOO mixed into one giant purple blob.
Pre-heat the oven to 375F and line a baking sheet with parchment paper.
Take the dough out of the fridge, and (using damp hands), roll out the dough into 1/4 inch thickness, and using a small glass, press in the dough to make circular cut-outs.
Stretch the dough a bit (if it's too dry, add a touch more water), and add a tsp of filling right in the center of the circle - if ever in doubt, add less filling than you'd think - you don't want to over-stuff the hamantashen.
Fold up the sides to make a triangle and place on the parchment paper.
Cook for about 15 minutes, until golden brown and crispy - but watch the oven carefully so they don't get too dark.
Let cool and devour!