In a small bowl, season the ground turkey with the garlic powder, half of the sea salt, and half of the black pepper.
Form the turkey into a wide, flat patty slightly larger than the English muffin.
Heat a non-stick skillet over medium heat with half of the olive oil and cook the turkey patty for 4-5 minutes per side until fully cooked through.
While the turkey cooks, whisk the whole egg and egg whites together in a bowl with the remaining salt and pepper.
Remove the turkey from the pan and set aside; wipe the pan and add the remaining olive oil.
Pour the egg mixture into the pan, tilting to cover the bottom, and cook until set; fold the edges in to create a square or circle that fits the muffin.
Place the spinach in the pan for 30 seconds just to wilt it slightly.
Split and toast the English muffin until golden brown.
Assemble the sandwich by placing the turkey patty on the bottom muffin, followed by the folded egg, cheddar cheese, and wilted spinach.
Top with the remaining muffin half and serve immediately while the cheese is melted.