Preheat and prep: Heat the oven to 350°F (175°C). Grease an 8x8-inch or 9x9-inch baking dish.
Blend the base: In a blender, add cottage cheese, Greek yogurt, eggs, oats, maple syrup or honey, vanilla, cinnamon, baking powder, salt, and lemon zest (if using). Blend until mostly smooth.
A few oat bits are okay.
Fold in blueberries: Pour the batter into a bowl and gently fold in 1 cup of blueberries. Reserve 1/2 cup for the top.
Assemble: Pour the batter into the baking dish. Scatter the remaining blueberries and nuts (if using) over the top.
Bake: Bake for 35–45 minutes, until the center is set and the top is lightly golden.
A toothpick should come out with a few moist crumbs but not wet batter.
Rest and slice: Let it cool for 10–15 minutes. It will firm up as it rests. Slice into 6–9 pieces, depending on your preferred portion size.
Serve: Enjoy warm as-is, or top with a spoonful of Greek yogurt, a drizzle of maple syrup, or a sprinkle of lemon zest.