Preheat the oven to 325ºF and lightly grease a non-stick muffin pan. In a large bowl, whisk together the almond flour, powdered sweetener, salt, and xanthan gum. Stir in the egg and melted butter until the dough comes together. Split the dough into two portions. Dust a work surface lightly with more almond flour and transfer one portion of the dough to the work surface. Cover the dough with waxed paper or parchment paper and roll out to an even 1/8″ thickness. Cut out into 3½ inch circles (cookie or biscuit cutters work, as does a drinking glass). Use an offset spatula to carefully lift each crust off the work surface. Press the crusts carefully down into the prepared muffin cups. If they crack at all, use a little extra dough to patch the crack. Repeat with the other half of the dough, then gather the scraps and re-roll to get more circles. You should be able to get at least 12 crusts. Bake the crusts for 12 minutes, then remove and let cool completely to firm up. Combine the butter and sweeteners in a medium saucepan over medium heat. Bring to a boil and cook for 3 to 5 minutes, watching carefully to make sure it doesn’t burn. Remove from heat and add the heavy cream and caramel extract. (The mixture will bubble vigorously, this is normal). Sprinkle the surface with the xanthan gum and whisk vigorously to combine. Whisk in the salt. Let cool to lukewarm, about 10 minutes. Once cooled, whisk in the egg. Divide the chopped raisins or pecans among the tart shells and spoon the filling over top. Fill each crust almost all the way to the top. Bake for 15 to 20 minutes, until the tart edges are golden and the filling is mostly set with a little jiggle in the center (it should still look a little wet in the very center of each tart). Remove from oven and let cool completely, then use a knife to loosen each tart.