Sandwich me Tono (Τόνο) is the canned-tuna sandwich of the Greek counter case, built cold and sold nationally beside the egg, chicken, and ham-and-cheese. The angle is that this is the most variable of the cold fillings to get right, because canned tuna is the cheapest of them and the one most often handled lazily. A good tuna sandwich here is a small, real pleasure; a bad one is wet, fishy, and slumped, and the difference is almost entirely in the drain and the mix.
The build is short and the early steps decide it. The tuna is drained well, then either left in flakes or bound with mayonnaise into a moist but not soupy mix. Counters fold in chopped onion, sweetcorn, a little lemon, sometimes capers or pickle. This goes into a soft roll or sliced loaf, usually over a leaf of lettuce and a couple of rounds of tomato. Good execution means tuna drained until it is no longer weeping, bound with just enough mayo to hold, brightened with acid and seasoned, and bread that stays intact long enough to eat. Sloppy execution is undrained tuna soaking the bread from below, a mix so heavy with mayo it slides out, no lemon or salt so it reads flat and fishy, and tomato cut thick enough to flood whatever the tuna did not. Drainage is the single discipline that separates a good counter from a careless one.
It shifts mostly through the mix-ins. The plainest version is drained tuna with mayo and onion. Sweetcorn is extremely common and pushes it sweeter and softer. Some counters add chopped boiled egg, edging it toward a fuller salad in bread; others keep it lean with just lemon, oil, and a few capers. A tuna salad served as a plate with greens rather than in bread is a different format and deserves its own article rather than being crowded in here. As a sandwich, Sandwich me Tono is dependable when the tuna is drained and balanced with acid, and grim when it is not.