Brian Earl Spilner said:
It's objectively the correct order.
Perhaps, but perhaps not. Let me make a case for the opposite.
Buns toasted in tallow
Bottom bun - topped with shredded lettuce and pickles on top of the lettuce. This will help capture some of the drippings and moisture, preventing the bottom bun from becoming soggy. For those who consider this a "salad" on the burger, well...grease and the vinegar from mustard and pickles combine to produce a sort of vinaigrette, no?
Beef Patties - onions smashed into the patty, then topped with mustard before flipping. Cheese melts on top.
Top bun - Here's where the mayo goes and ultimately gets a little melted to combine with the burger juices for absolute deliciousness.
For your visual representation:
