Combine butter and sweeteners in a medium saucepan over medium heat. Bring to a boil and cook about 3 minutes. If using all Swerve, you may find that your caramel recrystallizes a bit.
Add heavy cream and vanilla extract. Mixture will bubble vigorously, this is normal. Sprinkle with xanthan gum and whisk vigorously to combine. Stir in salt.
Let cool to lukewarm and then whisk in water.
Preheat oven to 350F.
Combine almond flour, coconut flour, sweetener, xanthan gum and salt in the bowl of a food processor. Pulse to combine.
Sprinkle surface with butter pieces and pulse until mixture resembles coarse crumbs.
With processor running on low, add ice water, one tablespoon at time until dough begins to clump together.
Place a large piece of parchment on work surface and dust liberally with additional almond flour. Turn out dough and pat into a rough circle. Sprinkle with more almond flour and cover with another large piece of parchment.
Roll dough out to about 1/8 inch thickness and remove top piece of parchment. Use a 3 to 3.5-inch diameter cookie cutter (or a glass; I used a wine glass) to cut out 12 circles, rerolling scraps as necessary.
Gently lift circles of pastry from bottom parchment with a knife or offset spatula and place in cavities of a standard muffin tin.
Place muffin tin in freezer while preparing the filling.
In a medium bowl, whisk together caramel sauce, powdered sweetener, egg, and melted butter.
Divide chopped raisins and filling among tart shells and bake 12 to 15 minutes, or until tart edges are just golden brown and filling is slightly puffed and mostly set. It should still jiggle just a little in the center of each tart.