In a large bowl, crack 18 eggs and add 1/3 cup cottage cheese. Season with salt and pepper. Whisk well and set aside.
In a large pan or skillet over medium high heat, cook ground sausage until brown and no longer pink, breaking apart into small pieces with the end of your spatula. Once cooked, remove the meat, drain some grease, and set the meat aside.
In the same pan over medium heat, add diced onion and tomatoes. Sauté for 1-2 minutes and season with salt and pepper. Add chopped spinach and cook until wilted. Once everything is cooked, set aside.
In the bowl of whisked eggs, add cooked sausage, and sautéd veggies. Stir to combine.
Grease a sheet pan with butter then pour in the egg mixture flat on the pan. Season the top of the egg mixture with Greek seasoning.
Place the sheet pan into the oven to bake for about 20 minutes.
Once the egg is cooked through, remove from the oven and slice into squares.
Serve immediately or wrap them individually in parchment paper or foil to store in the freezer for up to 3 months.
Note: to reheat, unwrap the frittata and place it into a damp paper towel. Microwave for 2-3 minutes and enjoy!
