Make the crust: In a bowl, stir together almond flour, melted butter, powdered sweetener, cinnamon, and salt until the mixture looks like damp sand and holds together when pressed.
Portion the crust: Divide the crust evenly among 6 to 8 small dessert cups or jars. Press it down gently with the back of a spoon to form a firm base. Chill while you make the filling.
Whip the cream: In a cold mixing bowl, beat the heavy cream to stiff peaks.
Set aside.
Blend the cream cheese: In another bowl, beat the softened cream cheese with powdered sweetener, vanilla, lemon zest, and a pinch of salt until smooth and fluffy.
Fold it together: Gently fold the whipped cream into the cream cheese mixture in two additions. Stop when it’s smooth and airy.
Make the blueberry layer: In a small saucepan over medium heat, add 1 cup of the blueberries, water, sweetener, and lemon juice. Cook 3 to 5 minutes, stirring, until some berries burst and release juices.
Thicken (optional): Sprinkle in xanthan gum very lightly while whisking to avoid clumps.
Simmer 30 seconds more until slightly thickened. Remove from heat and stir in remaining 1/2 cup fresh blueberries. Let cool to room temperature.
Assemble: Spoon the cream filling over the chilled crusts, leaving room on top for the blueberry layer.
Smooth the surface.
Add blueberries: Spoon the cooled blueberry mixture over the cream layer. Swirl gently with a toothpick if you like a marbled look.
Chill and serve: Cover and refrigerate at least 2 hours, or up to overnight, so the layers set. Garnish before serving with extra blueberries or mint.