Make the cinnamon crumble. In a bowl, whisk almond flour, protein powder (if using), sweetener, cinnamon, and salt. Stir in melted butter and vanilla until clusters form.
Set aside. It should be sandy with some small clumps.
Whip the cheesecake base. In another bowl, beat softened cream cheese until smooth. Add Greek yogurt, protein powder, powdered sweetener, vanilla, cinnamon, and a pinch of salt.
Whip until silky and thick. Taste and adjust sweetness or cinnamon.
Mix the icing. In a small bowl, whisk powdered sweetener, vanilla, a pinch of salt, and just enough milk to make a thick but drizzleable icing. You want it to hold faint lines when drizzled.
Layer the jars. Add 1–2 tablespoons crumble to the bottom of each jar.
Spoon or pipe a layer of cheesecake filling. Repeat with more crumble and more filling to create 2–3 layers, ending with a smooth top.
Add the swirl. Drizzle icing in a spiral or crisscross on top. For a classic cinnamon roll look, start in the center and spiral outward.
Chill to set. Cover and refrigerate for at least 1 hour, ideally 2–3 hours, to let the flavors meld and the filling thicken.
Serve. Top with a light dusting of cinnamon or a few extra crumble bits.
Enjoy straight from the jar.