Preheat a large non-stick skillet, indoor grill pan or tabletop grill to medium-high heat.
Combine ground turkey, finely chopped onion, cheddar cheese, chili powder, ground cumin, jalapeño or serrano, garlic, salt and pepper in a medium bowl and mix everything together with your hands. Score the meat with the side of your hand to separate into 4 equal amounts. Form mixture into 4 large patties no more than 1-inch thick. Drizzle EVOO on the patties and place patties in a hot skillet or on a hot grill and cook 5-6 minutes on each side or until turkey is cooked through.
For the cilantro cream, combine the sour cream and chopped cilantro, salt and pepper in a small bowl.