Preheat your oven to 325°F and line a large rimmed baking sheet with unbleached parchment paper.

In a large bowl with a handheld mixer, beat the butter until creamy (about 2 minutes).

Add in the egg yolk, confectioners’ sugar, vanilla, and salt. Beat until well combined (about 1 minute).

Mix in the flour and xanthan gum until fully combined; the dough should be thick but not stiff.

Scoop about 1 tablespoon of dough with a small cookie scoop or two spoons, placing mounds 1 1/2 inches apart on the baking sheet.

Roll each mound into a ball, coat lightly in granulated sugar, and place back on the sheet.

Use your finger or a dowel to poke a 1/2-inch wide, 3/4-inch deep hole in the center of each ball. Fill the wells with your favorite jam flavor or leave them empty for ganache.

Bake in the preheated oven until lightly golden, about 12-15 minutes.

Allow to cool before serving.