Heat your oven to 300°F. Line a baking sheet with parchment paper.
Add the egg white and cream of tartar to a mixing bowl. Use a hand mixer to beat the egg white until it's fluffy and holds soft peaks.
In a second bowl, whisk together the almond flour, sugar, and salt. Mix in the beaten egg whites to form a sticky dough -- it's ok if the eggs whites deflate while mixing.
Sprinkle the confectioner's sugar onto a cutting board or plate.
Divide the dough into 6 portons. Dampen your hands to eep the dough from sticking to them, then roll each piece of dough into a ball. Roll the ball over the confectioner's sugar to coat it lightly, then place it on the prepared baking sheet.
Press your thumb into the top of each cookie to create a divot. Fill each divot with 1/2 teaspoon of preserves.
Bake for 21-23 minutes, or until the tops of the cookies are firm and the bottoms are very lightly browned.
*Be sure to check the label of your confectioner's sugar to ensure it's gluten-free, if that's a concern for you or your guests. Many brands include additional starches that may contain gluten.