To top this burger, I personally like to use mayonnaise, lettuce and the grilled onions. My favorite gluten-free bun is this one!
Gently massage ground beef, sour cream, thyme, rosemary, parsley, black pepper, and salt until just incorporated. Divide meat into four portions. Flatten each portion to 3/4-inch thick. Gently press center of patty down to create a slight depression, about 1/2-inch diameter. Cover and chill patties 1 hour and up to 8 hours.
Coat red onion slices with coconut oil and sprinkle with salt and pepper. Remove patties from refrigerator and grill to desired doneness. While the patties are grilling, also grill the onion slices until they are turning golden brown on the edges.
Serve hamburger on gluten-free bun (or the bun of your choice) and topped with red onions and any condiments of your choice.