Prep your tools and oven. Preheat the oven to 350°F (175°C). Line a baking sheet with parchment paper. Set out two sheets of parchment for rolling the dough.

Mix the dry ingredients. In a bowl, whisk 2 cups almond flour, 2 tablespoons coconut flour, 1/3 cup powdered sweetener, 1/2 teaspoon baking powder, 1/4 teaspoon xanthan gum (optional), and 1/4 teaspoon salt.

Cut in the butter. Add 6 tablespoons cold, cubed unsalted butter. Use a pastry cutter or your fingers to work it in until the mixture looks like coarse crumbs.

Bind the dough. Whisk 1 egg with 1 teaspoon vanilla extract. Add to the bowl and mix until a soft dough forms. If it’s too dry, add 1–2 teaspoons cold water. If it’s sticky, chill for 10 minutes.

Roll it out. Place the dough between two sheets of parchment. Roll into a rectangle about 1/8 inch thick. Trim edges to even it out. Aim for 8 rectangles (about 3 x 4 inches each).

Prepare the filling. Stir 1/3 cup sugar-free jam until smooth. If too thick, warm it for a few seconds in the microwave. You want it spreadable, not runny.

Assemble the tarts. Transfer half the rectangles to the lined baking sheet. Add about 1 tablespoon of jam to the center of each, leaving a small border. Brush edges lightly with egg wash (1 egg beaten with 1 tablespoon water).

Seal and vent. Place the remaining rectangles on top. Press edges to seal, then crimp with a fork. Use a toothpick to poke 2–3 small vents on top to release steam.

Bake. Brush the tops with egg wash. Bake 14–18 minutes, until lightly golden around the edges. Let them cool on the tray for 10 minutes, then transfer to a rack.

Make the glaze. In a small bowl, mix 1/2 cup powdered sweetener with 1–2 tablespoons heavy cream or almond milk and 1/4 teaspoon vanilla. Add a few drops of lemon juice if you like a hint of tang. Adjust liquid for a spreadable consistency.

Glaze and set. Spoon or drizzle the glaze over cooled tarts. Let it set for 15–20 minutes before serving.