Preheat the oven to 375 degrees F.
Add the butter to a 9-inch round baking dish, or deep-dish pie plate, and place it in the oven as it’s warming up. Remove once the butter has completely melted. Tilt the pan around to coat the baking dish with the melted butter thoroughly.
Trim the ends of the squash and run the zucchinis through a vegetable spiralizer. I used the straight blade, but any will work.
Whisk together eggs, milk, sour cream, salt, and black pepper. Then mix in the cottage cheese.
Add the spiralized zucchini noodles (zoodles) to the baking dish. Pour in the egg mixture, whisking as you go, to evenly distribute the ingredients.
Place the baking dish back in the oven and bake for about 30 minutes, checking on it after 25 minutes. When the casserole is ready, it should be browned around the edges, and a toothpick inserted into the center should come out clean. There might be a few bits of cottage cheese on the stick, but that is okay.
Cool for 10 minutes before serving.