Tuna Salad Sandwich

Method

1. prep3 min
   press in the lid or a sieve
   tuna, drained until it stops weeping — every teaspoon of can liquid left behind thins the mayonnaise, and thin mayonnaise migrates straight into the crumb, which is the whole mechanism of a soggy sandwich
2. mix1 min
   in the bowl before the fish
   mayonnaise + dijon + lemon juice + salt + pepper, whisked smooth first — dressing built on top of the tuna needs stirring that breaks the flakes down, dressing built beside it does not
3. fold2 min
   gentle, few strokes
   + drained tuna + celery + red onion, turned over just until coated; stop while the flakes are still visible, since the celery's crunch and the tuna's grain are the only texture the sandwich has = tuna salad
4. rest5 min
   cold, uncovered
   tuna salad, so the salt draws a little liquid out of the onion and celery and the dressing tightens back up around the flakes; taste again here, because chilled salt reads weaker than room-temperature salt
5. toast3 min
   medium, until dry and pale gold
   bread slices — toasting sets a stiff crust that resists the dressing far longer than fresh bread, which collapses within minutes
6. top1 min
   assemble and cut immediately
   toast + lettuce leaf laid flat as a waterproof layer + tuna salad spread to the edges + second lettuce leaf + top slice; the leaf on each face is a barrier, not a garnish, and skipping it is why the bottom slice goes translucent