The afternoon-tea tomato sandwich is the same fruit as the everyday version put through a different set of manners. The defining facts are what has been taken away: the crusts, the thickness, the bulk. Thin slices of soft white bread are buttered edge to edge, given a single layer of tomato, pressed, trimmed square, and cut into small fingers or triangles meant to be eaten in two bites without a plate and without interrupting a conversation. It is the tomato sandwich made small and quiet on purpose. The trimming is not decoration; it is the design, because a crust would resist a delicate filling and the entire register depends on nothing resisting.
The craft is moisture control taken further than the kitchen version bothers with, because this sandwich has to survive the gap between the plate being made up and the tray reaching the table. The tomato is sliced thin, salted, and drained properly so the juice runs off well before it meets the bread, since a wet patch shows immediately on a pale crustless finger and there is no thick filling to disguise it. The butter is spread right to the edges as a deliberate waterproof layer between fruit and crumb. The tomato goes on in a single restrained layer rather than a generous one, because the point of the form is delicacy and balance rather than abundance, and an overloaded finger collapses when picked up. Plain soft bread is correct precisely because it offers no chew to fight a soft filling.
There is not much to vary here without leaving the form. A turn of white pepper, the thinnest possible basil leaf, or a wisp of cream cheese under the tomato is about as far as the register stretches before it becomes a different sandwich. The hearty everyday tomato sandwich, thick-cut and salted at the counter, is the other reading and is treated on its own. Each deserves its own article rather than being crowded in here.