Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking dish with cooking spray or olive oil.

In a large mixing bowl, whisk together the eggs, almond milk, garlic powder, onion powder, salt, and black pepper until well combined.

In a skillet over medium heat, cook the breakfast sausage until browned and fully cooked, breaking it apart with a spatula as it cooks. Drain any excess fat.

Add the diced bell peppers, onion, and spinach to the skillet with the sausage and cook for an additional 3-4 minutes until the vegetables are tender.

Spread the sausage and vegetable mixture evenly in the prepared baking dish. Pour the egg mixture over the top, ensuring it covers all the ingredients. If using, sprinkle the dairy-free cheese on top.

Bake in the preheated oven for 30-35 minutes, or until the casserole is set in the center and lightly golden on top.

Allow the casserole to cool for 5-10 minutes before slicing and serving.