To prepare the toppings, slice the onion and tomatoes into rings.

Mix the oil, vinegar, salt, pepper, and mustard well, and marinate the onion and tomato rings in the mixture to absorb the flavor.

To prepare the burger, grate the onion and add half a teaspoon of salt, then let it sit for 10 minutes to release the onion juice, then drain completely.

Take the drained onion and add it to the beef with the remaining ingredients, and mix well.

Shape the meat into burger patties, preferably with a medium thickness. After shaping, it's best to refrigerate them for 30 minutes.

Fry the burger patties in a pan with hot oil on both sides until they are browned and the meat is sealed.

Place the burger patties on a pizza tray and bake in a preheated oven at 250°C (about 480°F) for 25 minutes.

Split the burger buns in half, spread the bread sauce on both halves, and place a slice of tomato and a slice of onion on each half with a burger patty in between.

Top the burger with a tablespoon of cheddar cheese sauce and serve.