Preheat and prep: Heat the oven to 350°F (175°C).
Lightly grease an 8x8-inch baking dish with butter or coconut oil.
Blend or whisk the base: For extra smoothness, blend 1 1/2 cups cottage cheese with 3 eggs, 1/2 cup milk, 1/4 cup maple syrup, 1 teaspoon vanilla, 1 teaspoon lemon zest, 1 teaspoon cinnamon, 1 teaspoon baking powder, and a pinch of salt. No blender? Whisk well; small curds are fine.
Add the oats: Stir in 1 cup rolled oats until evenly coated.
Let it sit for 3–5 minutes to hydrate slightly.
Fold in blueberries: Gently fold in 1 1/2 cups blueberries. If using frozen, add them straight from the freezer and toss lightly to avoid streaking.
Assemble: Pour the mixture into the prepared dish. Smooth the top.
Sprinkle with a few extra blueberries and, if you like, 2 tablespoons sliced almonds or walnuts for crunch.
Bake: Bake for 35–45 minutes, until the center is set and the top is lightly golden. A knife inserted near the center should come out mostly clean.
Rest and serve: Let it cool for 10 minutes to set. Serve warm as is, or add a dollop of yogurt, a drizzle of maple syrup, or a dusting of cinnamon.