The whole sandwich turns on a single timed step: how long the bread spends under water before the tomato goes on. A frisella is a Puglian ring of bread baked, sliced through its equator, and baked again until it is rock-hard and dry, a loaf engineered to keep for weeks in a hot, dry climate where fresh bread does not last. It is inedible as it comes. To make it a sandwich you hold it briefly under water, just long enough that the outside yields and the inside stays firm, then crushed ripe tomato is rubbed and pressed over it with olive oil, salt, and oregano so the tomato's own juice finishes the softening from above. Get the dip right and the frisella is tender at the surface and still has spine in the middle; get it wrong and it is either a cracker or a sponge.
The craft is that revival and the restraint that follows it. The dunk is counted in seconds, not left to soak, because a frisella given too long collapses into wet paste and a frisella given too little stays a brittle disc that scrapes the mouth. Once it has taken just enough water, the topping is kept deliberately spare: tomato crushed by hand so its juice runs into the bread, a hard pour of olive oil, coarse salt, and dried oregano, and nothing more, because the point is to taste a revived bread and a ripe tomato rather than to bury either. It is dressed and eaten promptly, while the contrast between the softened rim and the firmer centre is still there and before the whole ring slumps. Served open, it is one slice carrying one idea.
The variations stay in Puglia and stay simple: the version with rocket or a few olives worked in against the tomato, the one rubbed with garlic before the oil, the wheat frisella against the darker barley one, which drinks water differently and wants a shorter dip. Those bread choices each change the timing. Each of them deserves its own article rather than being crowded in here.