Preheat the oven to 375°F.
Grease a 9x13 inch baking dish thoroughly with nonstick cooking spray, including the sides and corners.
Blend the cottage cheese with an immersion blender until completely smooth, about 30 seconds. (A regular blender or food processor also works.)
In a large mixing bowl, whisk the eggs with the garlic powder, salt, and black pepper until fully combined.
Add the blended cottage cheese and Parmesan to the eggs and whisk until creamy and cohesive.
Fold in the chopped spinach and onion until evenly distributed.
Pour the mixture into the prepared baking dish and spread evenly.
Bake uncovered for 30 to 35 minutes, until the center is set and the top is lightly golden. A toothpick inserted in the center should come out clean.
Let the bake rest for at least 10 minutes before slicing for cleaner portions.
Slice into 6 portions, cool completely, then transfer to individual snap-lock containers and label with the date.