Whisk together coconut oil, maple syrup, one egg, and fine sea salt in a large bowl.
Add in almond flour, tapioca flour, and baking powder and combine together thoroughly with a sturdy spoon until the dough is well hydrated and no dry spots remain.
Transfer the dough to plastic wrap, and chill, for at least an hour or up to 1 day.
Preheat the oven to 350ºF and line a baking sheet with parchment paper and set aside.
Set out a large piece of parchment and sprinkle it with tapioca flour. Set the dough in the middle of the parchment and sprinkle the top with tapioca flour too. Roll out the dough to a thickness of 1/4 - 1/8 of an inch.
Stamp out 3" circles using a cookie cutter. Re-roll the scraps up to two times. You should get about 18 circles.
Transfer the cookies to the prepared baking sheet. If any of the dough sticks to the parchment, run a small spatula dusted with tapioca flour underneath the dough to loosen it.
Make an egg wash by whisking together the remaining egg with 1 teaspoon of water. Brush each circle with egg wash and place 1 teaspoon of jam in the center of each circle.
Form the circles into triangles by gently folding over one side and pinching together the corners where they meet. Repeat for the other sides.
Once all the cookies are formed, refrigerate for 15 minutes to chill. This helps the cookies keep their shape better.
Brush the chilled cookies with egg wash on the outside and then bake on the middle rack for 13-15 minutes, until lightly browned on the bottom.
Transfer to a wire rack to cool slightly before enjoying.