In a small bowl, mash the avocado, sour cream, cilantro, and garlic together with a fork until combined but still a bit chunky. Season with salt to taste. Store in the fridge until ready to serve.
In a medium mixing bowl, combine the ground turkey, salt, cilantro, salsa, and bread crumbs until evenly combined. Use your hands to divide into 4 equal portions and then form into burger patties.
Place a large non-stick skillet over medium-high heat. Add the burger patties and cook for 5 minutes.
Flip the burgers. Then top each one with a slice of pepper jack cheese. Cook for another 5 minutes until the burgers are cooked through, and the cheese has melted.
To serve: Add a couple of slices of red onion on the bottom burger bun. Then add the turkey burger, a couple of tomato slices, and then a big dollop of the avocado sauce. Serve warm.
Notes
You can add some pepperoncini on top of the turkey burger for a little extra zip if you like.
For a low-carb option, skip the burger bun and layer the onions and tomatoes on top of the patty before topping with sauce. Then grab a fork and knife and dig in.