In a medium bowl, whisk together the almond flour, sweetener, and salt. Stir in the melted butter until the dough resembles coarse crumbs.
Turn the loose dough out into a 9-inch ceramic tart pan. Press firmly into the bottom and up the sides. Use a flat-bottomed glass or measuring cup to even out the bottom of the crust. Prick all over with a fork.
Par-bake for 10 minutes, then remove from the oven and cool while you prepare the filling.
To make the filling:
In a food processor or high powered blender, combine the ricotta, cream cheese, eggs, powdered sweetener, granulated sweetener, and vanilla extract. Process on high until the mixture is smooth. Stir in the chocolate chips.
Pour the batter into the par-baked tart crust. Set the tart pan into a large roasting pan and fill the roasting pan with water until it reaches halfway up the sides of the tart pan.
Carefully place the roasting pan into the oven and bake for 60 to 75 minutes, or until the filling is just set. Cover the edges of the crust with strips of tinfoil if they are browning too quickly during baking.
Remove the tart from the water bath and let cool 20 minutes. Refrigerate until firm, at least 1 hour and up to overnight, before serving.
To make the chocolate drizzle:
Place the chopped chocolate and butter in a heat-proof bowl set over a pan of barely simmering water. Stir until melted and smooth.
Drizzle the chocolate over the chilled tart, and slice into 12 pieces.
Serving: 1/12th of tart | Calories: 257kcal | Carbohydrates: 7.61g | Protein: 8.55g | Fat: 21.25g | Fiber: 3.16g