Fire up your grill to medium-high heat, around 375-400°F (190-205°C)

Divide your ground beef into 4 evenly sized portions, each weighing approximately 6oz

Form each portion into a loose ball. Gently flatten each ball into a disc-shaped patty. Use your thumb to make a small indent into the center of each patty. Season both sides with kosher salt.

Once grill is warmed up, carefully arrange patties on grill grates. Ensure they are not touching.

Grill for 5 minutes. Flip each patty and grill for a further 3-5 minutes, until internal temperature is 160°F (71°C).

If you are adding cheese to your burgers, do this during the last 2 minutes of grilling so that the cheese has a chance to melt.

Remove the burgers from the grill and allow them to rest for 5 minutes before serving

While the burgers are resting, add canola oil to cast iron skillet and place on grill grates, directly over heat

Add onion slices to the skillet and cook until they start to caramelize, about 3-5 minutes

Assemble your burgers with caramelized onions and your favorite toppings. Serve and enjoy.