Preheat the oven to 350 degrees. Line the bottom of a 9-inch tart pan (or three 5-inch tart pans) with parchment paper. Grease the sides with oil.
In a small food processor, pulse the almond flour and the salt until combined. Add the coconut oil and egg and pulse a few more times until a dough forms. Warning: it will be very sticky.
Transfer the dough to the center of the tart pan(s). Using a sheet of plastic wrap or greased palms, press the dough out into an even crust, about ¼ inch thick. Bake in the oven for 8 to 10 minutes, until firm an beginning to brown. Remove and let cool.
Meanwhile, make the filling: in a blender or food processor, puree the avocado, lime juice and zest, maple syrup and coconut oil until smooth.
Pour the avocado mousse into the cooled tart shell(s) and smooth into an even layer. Transfer to the refrigerator to set, at least 1 hour, or overnight.
To serve, spoon the vanilla skyr on top and garnish with a slice of lime.