01 - Preheat oven to 350°F (180°C). Lightly grease a 12-cup muffin tin or line with silicone liners.
02 - In a skillet over medium heat, cook turkey sausage, breaking it up with a spatula, until browned and fully cooked. Drain off any excess fat.
03 - Add red bell pepper and spinach to skillet. Sauté for 2 to 3 minutes until vegetables are softened. Remove from heat and allow mixture to cool slightly.
04 - In a large mixing bowl, whisk together eggs, milk, garlic powder, paprika, salt, and pepper until fully combined.
05 - Stir cooled sausage and vegetable mixture, green onions, and shredded cheddar cheese (if using) into eggs. Mix until evenly distributed.
06 - Evenly divide the mixture among the muffin cups, filling each about three-quarters full.
07 - Bake for 20 to 25 minutes, or until the muffins are set and lightly golden on top.
08 - Let muffins cool in the pan for 5 minutes, then remove. Serve warm, or allow to cool completely for storage.