Combine almond flour, arrowroot starch, and sea salt in a food processor and pulse a few times to combine.
Add cold butter and pulse several times until crumbly.
Add in an egg, maple syrup, and apple cider vinegar and pulse again until the dough sticks together when you pinch it.
Wrap the dough in a plastic wrap and flatten it out into a disc.
Refrigerate for 1 hour.
While the dough is chilling, combine all ingredients for the filling in a large bowl and stir together.
Once the dough is ready, preheat oven to 375 degrees F.
Place the dough between 2 parchment papers and roll into a circle about 1/4 inch thick. Remove the top parchment paper.
Place the cranberry filling in the center of the dough in an even layer, leaving about 2 inches around the edges.
Use the bottom parchment paper to fold the dough over the edges of the filling, sealing the dough with your fingers if it rips.
Brush the whisked egg yolk on the dough edges.
Slide the parchment paper with the cranberry galette onto a baking sheet.
Bake for 35 minutes.
Cool for 5 minutes before slicing and enjoying.