lemon meringue tart

In British English pie implies a top crust. The names of some traditional North American dishes, such as Pecan Pie, have been imported into the English language untranslated, much as Tarte Tatin still gets spelt with an 'e'. If pecans, pumpkins, or lemon meringues grew in the wild in Britain then those things would have been called tarts.

If a cobbler has a thick enough crust, of course, it becomes a crumble.

Peter