In N Out fans, here is a perfect copycat!

For 4 burgers, you need:

1 lb ground beef (I used 70% lean. Better is 60%.)
Salt and pepper for seasoning
1 tablespoon worcestershire sauce
Lettuce
Tomato, sliced
Red onion, sliced (I don't like raw onion in my burger, so I made caramelized "grilled" onion for my burger. To caramelize onion: add slices of one yellow onion to a sauté pan on medium-low heat with 1 tablespoon olive oil. Put the lid on the pan. Check every 10 min to see that the onions don't burn but get soft and caramelized. Takes about half and hour.)
4 or more slices of cheese (I used Kraft's American cheese)Special Pink Sauce (recipe below)
4 Hamburger buns

Special Pink Sauce (In n Out Burger copycat)

½ cup mayonaise (Hellman's mayonaise are gluten free)
¼ cup ketchup (Heinz Ketchup is gluten free)
¼ cup relish (gluten free)
⅛ teaspoon (a pinch) salt
⅛ teaspoon (a pinch) sugar
⅛ teaspoon (a pinch) onion powder
¼ teaspoon (2 pinches) garlic powder
½ tablespoon worcestershire sauce

How:

Add worcestershire sauce to ground beef and mix it well. Divide the meat in four portions and make patties. Make the middle of the patties thinner than the outside. This will prevent the patties from swelling up when cooking.

Put a pan on or griddle on medium-high heat. Cook one side of the patties for 3 min. Flip it over and cook for another 3-4 min. Place a slice of cheese on top and remove the patty when the cheese is melty.

For Pink Sauce:

Mix all the ingredients in a bowl. Store away the unused sauce in a jar in your refrigerator. It will have the same life as your ketchup or mayo.

Build your burger:

Top part of bun
Lettuce
Tomato
Caramelized onion
Cheese
Beef patty
Pink sauce
Lower part of bun

Source: HappilySpiced.com