In a medium mixing bowl, combine the oat flour, almond flour, melted butter or coconut oil, sweetener, vanilla, and a pinch of salt. Stir until the mixture forms a moist, crumb-like dough that holds together when pressed. Line your baking dish with parchment paper, then firmly press the crust mixture into an even layer across the bottom. Prebake the crust for 10 minutes at 325°F (160°C) until lightly set.

While the crust bakes, add the cottage cheese, Greek yogurt, eggs, protein powder, lemon zest, lemon juice, and sweetener into a blender or food processor. Blend on high until the mixture becomes completely smooth, creamy, and lump-free. Scrape the sides as needed to ensure everything is fully incorporated.

Pour the blended filling into a clean bowl, then add the blueberries. Gently fold them in using a spatula, being careful not to burst them. This helps maintain a clean, beautiful swirl pattern throughout the bars once baked.

Remove the prebaked crust from the oven and pour the cheesecake filling evenly over the top. Tap the pan gently on the counter to release any air bubbles. Return the dish to the oven and bake at 325°F (160°C) for 28–34 minutes, or until the edges are set and the center jiggles slightly when moved.

Allow the cheesecake to cool at room temperature for 1 hour. Once no longer warm, transfer the pan to the refrigerator and chill for 2–3 hours, or ideally overnight, to let the bars firm up completely. Slice into even squares and serve chilled for the best texture.