Preheat your oven to 350°F (175°C). Grease your baking dish with butter or nonstick spray.

Prepare the apple filling: Peel, core, and slice 4 medium apples into 1/4-inch thick slices. Toss them in a bowl with 2 tablespoons sugar, 1 teaspoon cinnamon, 1 tablespoon lemon juice, and a pinch of salt. Set aside.

Blend the cottage cheese in a blender or food processor for about 30 seconds until smooth and creamy.

In a large bowl, combine the blended cottage cheese, 1/2 cup Greek yogurt, and the apple mixture. Stir gently until well combined.

Make the crumble topping: In a separate bowl, mix 1 cup rolled oats, 1/2 cup almond flour, 1/3 cup vanilla whey protein powder, 1/4 cup melted butter, 2 tablespoons brown sugar, and 1 teaspoon cinnamon. Stir until the mixture forms coarse crumbs.

Pour the apple filling evenly into the prepared baking dish. Sprinkle the crumble topping generously over the apples, covering them completely.

Bake for 35-40 minutes until the topping is golden and crisp and the filling is bubbling around the edges.

Cool for 10-15 minutes before serving to allow the filling to set.