Preheat your oven to 375°F (190°C) and lightly grease a standard muffin tin with avocado oil or coconut oil spray.
In a small skillet over medium heat, cook the ground turkey until fully browned and crumbled, then set aside to cool slightly.
Finely dice the red bell pepper and roughly chop the fresh spinach into small ribbons.
In a large mixing bowl, whisk together the whole egg, liquid egg whites, and non-fat Greek yogurt until the mixture is completely smooth.
Add the oat flour, garlic powder, sea salt, black pepper, and baking powder to the wet ingredients, whisking until just combined.
Gently fold in the cooked ground turkey, chopped spinach, and diced bell peppers until evenly distributed throughout the batter.
Divide the mixture evenly among 4 to 6 muffin cups, filling them nearly to the top.
Sprinkle the shredded sharp cheddar cheese over each muffin for a savory finish.
Bake for 20-25 minutes, or until the muffins have risen and the cheese is melted and golden brown.
Allow the muffins to cool in the tin for 5 minutes before removing them to serve warm.