Preheat your grill to 400 degrees. Place a cast iron skillet on direct heat or a griddle and allow it to heat up.
Divide your meat into 4 and them form 4 balls of meat.
Mix together your salt and pepper.
Add the oil to the hot cast iron and allow it to heat.
Place a ball of meat on the hot skillet and then place a piece of wax paper over the top. Use your spatula or burger press to flatten it out evenly.
Sprinkle a little salt and pepper over the top.
Proceed with the remaining balls of meat, careful not to crowd the pan. You can work in batches if needed.
Let the first side cook for 2 minutes or until it's sizzling and brown.
Flip your burgers and top with cheese.
Let the second side cook until brown, about 2 minutes.
To assemble your burgers spread mayo over the bottom bun. Top with pickles. Add 1-2 burger patties on top and then spread the caramelized onions over it. Top with the top bun and enjoy!