Preheat oven to 325°F (160°C) and line an 8×8 baking pan with parchment paper.
In a bowl, mix almond flour, sweetener, lemon zest, and oil/Greek yogurt. Press the mixture firmly into the pan to form the crust. Bake for 8–10 minutes, then cool slightly.
Blend cottage cheese until completely smooth. Add Greek yogurt, protein powder, lemon juice, lemon zest, eggs, vanilla, sweetener, and salt. Whisk until creamy and lump-free.
Pour the filling over the crust. Tap the pan gently on the counter to remove air bubbles.
Bake for 28–32 minutes, or until the edges are set and the center has a light jiggle.
Cool at room temperature for 30–40 minutes, then refrigerate for at least 3 hours, preferably overnight.
Lift out using parchment paper and slice into 9–12 bars. Store chilled for up to 5 days or freeze for 1–2 months.