Preheat the oven to 325 F.
Combine the almond flour, 1/4 cup sweetener and 1/4 teaspoon salt in a large bowl.
Pour in the 1/4 cup of melted butter and stir until the dough forms coarse clumps.
Press the dough firmly into a pie plate with your fingers, working it up the sides.
Prick the base all over with a fork, then pre-bake for about 10 minutes, until it just begins to turn golden. Set aside to cool.
Melt the 3/4 cup of butter in a saucepan over low heat.
Stir in the 1 cup of sweetener until it dissolves, then take the pan off the heat.
Whisk in the vanilla and remaining salt, then let the mixture cool until it is warm rather than hot. This matters.
Whisk the eggs into the cooled mixture one at a time until smooth.
Spread the pecan halves over the cooled crust and pour the filling over them.
Bake for about 45 minutes, until the filling is set and no longer wobbles in the center.
Cool for at least 30 minutes before slicing so the filling firms up.
