Start by preheating your oven to 350°F.
Slice the peppers in half lengthwise and scoop out the seeds and ribs. Arrange them cut-side up on a baking sheet and bake for about 15 minutes, just until they start to soften.
While the peppers are in the oven, add the eggs, cottage cheese, salt, and pepper to a blender. Blend until completely smooth and creamy.
Once the peppers have softened, carefully pour the egg mixture evenly into each pepper half.
Sprinkle the tops with spinach, tomato, and onion, then finish with a generous layer of shredded mozzarella.
Return the pan to the oven and bake for another 20 minutes at 350°F, until the eggs are set.
Turn the broiler on high for 1–2 minutes at the end to get that golden, slightly bubbly top. Keep a close eye on it!
Garnish if you’d like, serve warm, and enjoy.