Originally Posted by
nkedel
At restaurants, I'll sometimes order "just meat and cheese," and once got asked "do you want a bun?" but I'm pretty sure it was waiter humor (like reading your order back with "and extra mayo" instead of "no mayo") and not an assumption that I was low-carbing it.
Not so sure it was a joke. There's been a lot more recognition of low carbohydrate diets in the past few years. Some restaurants have no-bun options listed on the menu, and plenty of others understand exactly what you mean when you ask for it without a bun.
Regarding the OP: I expect that "plain hamburger" means meat and bun anywhere in the USA. Though a bit of conversational context is important. For example, when the cashier asks, "Would you like to add cheese or sauteed mushrooms?" and the customer responds, "No, I'd like it plain," that's ambiguous. Probably the customer is simply saying no to the cheese and mushrooms.