First you need to prepare burger patties. Mix minced meat, egg, chopped onion, crumbs and seasonings. Minced meat must be thoroughly beaten off and formed into flat cutlets. I made them in specially designed silicone rings and pressed down with a press.
Grill cutlets on both sides. You can use a grill pan, I do it in an electric grill.
Now assembling the burger. Cut the bun. Put lettuce on the lower part, then two circles of tomato (if the tomato is large, then one), red onion rings, cutlet, sauce, pickled cucumber slices. Cover with the other half of the bun.