01 - Preheat oven to 350°F. 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 cooked through. Drain excess fat.
03 - Add red bell pepper and spinach to the skillet, sautéing for 2 to 3 minutes until vegetables are softened. Remove from heat and let cool slightly.
04 - In a large mixing bowl, whisk together eggs, milk, garlic powder, paprika, salt, and pepper.
05 - Add the cooked sausage and vegetable mixture, green onions, and shredded cheddar cheese (if using) to the egg mixture. Stir until evenly combined.
06 - Divide the mixture evenly among the 12 muffin cups, filling each about three-quarters full.
07 - Bake for 20 to 25 minutes, until set and lightly golden on top. Let cool for 5 minutes before removing muffins from the tin.
08 - Serve warm or let cool completely before storing in an airtight container.