n a large bowl, mix together the ground turkey, grated apple, Dijon mustard, dried thyme, onion powder, salt, and black pepper. Gently combine the ingredients with your hands until well blended. The mixture will be slightly moist. Form the mixture into 4 patties.
Preheat a nonstick skillet or grill pan over medium-high heat and apply a light coat of oil spray or nonstick cooking spray. Ensure the pan is hot before placing the patties in it to achieve a good sear and prevent sticking.
Cook the turkey patties on one side for 5 minutes. Flip the patties, lower the heat to medium, and cook for an additional 5 to 6 minutes, or until the internal temperature reaches 165ºF. In the last minute of cooking, place a slice of cheddar cheese on each patty.
For the mayo, whisk together the mayonnaise, Dijon mustard, and maple syrup until well combined.
Assemble the burgers on toasted brioche buns with green leaf lettuce, thin apple slices, and a generous spread of maple Dijon mayo.