from bottom to top:
>dry toasted bun
>patty with melted cheese
>second patty if you so choose, also with melted cheese
>lettuce (usually iceberg)
>raw onion (optional I guess, but cmon)
>light spread of mayo/horseradish mayo on dry toasted bun
the bottom dry toasted bun soaks up some of the burger juice but still maintains structural integrity. im not in favor of butter/mayo toasted for a burger because the smoother surface doesn't grip the ingredients as well.
when it comes to the patty, im personally am in favor of thin patties, cooked all the way through with lots of char on the outside. inb4 muh meedyum rar, ground beef isn't meant to be undercooked, as the texture just gets mushy and gross; I don't give a tin shit about the food safety aspect of it. it also keeps the option open for a double cheeseburger. I usually just salt and pepper the outside, though I've occasionally smeared mustard on the outside à la in-n-out and had good results with that.
the iceberg lettuce is there for texture and crispness to counteract the heft of the beef. the star of the show is always the patty, and getting funky with your greens choice usually takes away from that. the cheese on the lettuce directly provides a good anchor so it doesn't slip around as much. raw onion provides additional crunch and a nice bite to balance that strong beef flavor; the horseradish does the same.
thats my template burger. when you do fool around, it's important to remember where stuff is placed, because nothing is more disappointing than a burger where all the toppings have gooped out. also, meme burgers with 5+ toppings, to what end?