Prep the pan: Lightly grease a 9x13-inch baking dish.
Preheat oven to 375°F (190°C).
Cook the veggies and sausage: In a large skillet over medium heat, sauté the onion and red bell pepper with a pinch of salt until softened, about 5 minutes. Add the cooked sausage to warm through. Stir in spinach until wilted.
Remove from heat.
Whisk the eggs: In a large bowl, whisk eggs, egg whites (if using), cottage cheese, garlic powder, cumin, smoked paprika, salt, and pepper until evenly combined.
Scramble gently: Pour the egg mixture into the skillet with the sausage and veggies over medium-low heat. Cook, stirring slowly, until softly set. Keep the eggs slightly underdone—they’ll finish in the oven.
Mix the sauce: In a bowl, whisk enchilada sauce, Greek yogurt, lime juice, and chili powder until smooth.
Assemble the enchiladas: Warm tortillas briefly to make them pliable.
Spoon a generous line of the egg mixture down each tortilla, sprinkle with a little cheese, then roll snugly. Place seam-side down in the baking dish.
Top and bake: Pour the sauce evenly over the rolled tortillas and sprinkle with remaining cheese. Cover loosely with foil and bake for 15 minutes.
Remove foil and bake another 5–8 minutes, until bubbly and lightly golden.
Finish and serve: Rest 5 minutes. Top with cilantro, green onions, avocado, or salsa. Serve warm.