01 - Set oven to 350°F and lightly grease a 12-cup muffin tin or line with silicone liners.
02 - In a skillet over medium heat, cook turkey sausage, crumbling with a spatula, until browned and fully cooked. Drain excess fat.
03 - Add diced red bell pepper and spinach to the skillet. Sauté for 2 to 3 minutes until vegetables soften. Remove from heat and cool slightly.
04 - In a large bowl, whisk together eggs, milk, garlic powder, paprika, salt, and pepper until well combined.
05 - Fold the sausage mixture, green onions, and shredded cheddar cheese (if using) into the egg mixture, stirring until fully incorporated.
06 - Evenly divide the combined mixture among the muffin cups, filling each about three-quarters full.
07 - Bake for 20 to 25 minutes, or until the egg muffins are set and lightly golden on top.
08 - Allow to cool for 5 minutes before removing from the tin. Serve warm, or cool completely for storage.