In a bowl, combine lean ground turkey with finely chopped fresh spinach, garlic powder, salt, and pepper. Mix until evenly distributed.
Form the mixture into a patty.
Heat a non-stick skillet over medium heat and add olive oil. Once heated, cook the turkey patty for about 4-5 minutes on each side or until it reaches an internal temperature of 165°F.
While the patty is cooking, scoop the avocado into a small bowl, add lemon juice, a pinch of salt, and pepper. Mash until you achieve a creamy, spreadable consistency.
Toast the whole wheat burger bun lightly in a separate pan or toaster.
Assemble the burger by spreading the avocado mixture on the bun, placing the cooked turkey spinach patty on top, and finishing with any additional fresh spinach if desired.
Serve immediately and enjoy your lean, nutrient-packed burger.