Heat a skillet on medium high heat and melt the butter and corn oil.

Cook the onions for 15 - 20 minutes stirring occasionally.

Add 1/4 cup of water towards the end of cooking to pick up all the bits from the bottom of the pan.

Season the beef with the salt, pepper and seasoned salt.

Form into 8 patties.

Heat 1 tablespoon grape seed oil on medium heat.

Place the patties in the pan and cook for 4 minutes per side.

In the final minute of cooking, add 2 slices of the emmentaler and 1 slice of the gouda to the burgers. Cover with a top and cook for 1 - 2 minutes.

While the burgers are resting, butter one side of the rye bread.

Add the rye bread, butter side down, to the skillet and cook for 1 - 2 minutes until browned.

To serve, place the cheeseburger on the bread. Add as many grilled onions as you can fit.

Top with the 2nd piece of bread.

Serve and enjoy!