Well, I have to give y’all some important information that has been missed here, so far.
Inre ultrafilter’s “the more flavors, the better” theory: no, I must disagree. Here we are looking for a symphony, not a cacophony. We have a star performer and it’s the burger. Piling in more accompaniment will only confuse the issue.
Inre wump’s grinding up a baseball!? My God, man, you only get one or two of those per sirloin butt and their proper fate is to be grilled rare (or at most rare+). No, for a burger grind up some nice chuck yourself and you’ll be wondering what the Vons done the street has been selling you all these years.
To the OP: Form your patty about 1/2" oversize in diameter so that the shrinkage in the cooking proces renders a finished burger the same diameter as your bun and leaves the all-important meat/bun/trimmings ratio constant through the entire feast.
Nobody has mentioned this yet so I feel compelled to: the hamburger is a structure and as such order of assembly is vital. We don’t put our basements on top of our roofs now, do we? So, toast the bun lightly and place a single, full green leaf of iceberg lettuce folded to shape on the lower bun half. This will help protect the thin bread of that half from the dreaded “soaked-goo” syndrome that we all hate.
Dress your upper bun half with some Gulden’s mustard and just a little Heinz ketchup and just a little good mayo. The ripe tomato slice goes on next. While the burger is cooking, by the way, be sure to season with a little salt and a good dusting of fresh cracked black pepper. Cheese, if used, is added at the end of the grilling to only warm the cheese, not to melt the snot out of it.
So there you are with a prepped bottom and top bun and a cooked burger. Put the burger on the lower half and cover it with a generous slice of a sweet Walla-walla onion (they’re sweet and mild, so you can get away with a nice thick slice for texture), cover them all up with… Well I think you get my point.