Heat oven to 350°F and lightly grease a 9-by-13-inch baking dish.
Brown turkey sausage in olive oil, breaking into crumbles, until the largest piece reaches 165°F; transfer to a plate.
Sauté onion and pepper 6 to 8 minutes, add spinach and cook until wilted and the skillet is dry; cool 10 minutes.
Blend cottage cheese, Dijon, garlic powder, smoked paprika, salt and pepper for 30 to 45 seconds until smooth.
Whisk whole eggs and liquid whites gently until uniform, then whisk in blended cottage cheese without making foam.
Spread sausage and cooled vegetables in the dish, add 3/4 cup cheddar, pour in egg mixture and top with remaining cheese.
Bake 32 to 42 minutes, checking at 30, until the center no longer ripples and reaches 165°F.
Rest on a rack 15 minutes before cutting into eight portions.
