Make the crust: In a small bowl, mix almond flour, melted butter, sweetener, vanilla, and salt until it looks like damp sand. Divide evenly among 4 jars and press down lightly with the back of a spoon.
Set aside.
Prepare the blackberry layer: In another bowl, gently mash blackberries with sweetener and lemon zest. If you want a thicker, jammy texture, stir in chia seeds and let sit for 5–10 minutes to gel slightly.
Blend the filling: In a mixing bowl, beat cream cheese until smooth. Add Greek yogurt, protein powder, powdered sweetener, vanilla, lemon juice, and a pinch of salt.
Beat until creamy with no lumps. Taste and adjust sweetness or lemon.
Assemble: Spoon the cheesecake filling over the crust in each jar, leaving room for berries. Top with the blackberry mixture.
Swirl lightly with a spoon if you want a marbled look, or keep layers neat.
Chill: Cover and refrigerate for at least 1–2 hours, or up to 24 hours for the best set and flavor meld.
Serve: Garnish with a fresh blackberry and mint if you like. Enjoy straight from the jar.