This soup is lovely on nights when you need to sup on something light yet filling and when you feel like spending even less time on cooking than you ordinarily do. If I’m still hungry after this, I usually dig into a sandwich or whip up a salad.
Thinly slice the scallions including most of the green tops. Peel, halve, seed, and finely chop the cucumber. Quarter, seed, and chop the tomatoes. Thinly slice the radishes. Drain the tuna. Rinse and mince the cilantro.
In a medium-size saucepan, combine the scallions, cucumber, tomatoes, radishes, tuna, clam juice, and water. Cover the pan and bring the liquid t