Set up your cutting board and slice the radishes thinly using a chef's knife, aiming for uniform, translucent pieces that showcase their peppery texture.
In a large mixing bowl, combine the mixed greens and sliced radishes, tossing gently to distribute the radish slices evenly among the greens.
Add the drained canned tuna to the bowl, breaking it up lightly with a fork to distribute evenly without losing all texture.
In a small bowl, whisk together the lemon juice, olive oil, and a pinch of salt and pepper until the dressing is well combined and slightly emulsified.
Pour the dressing over the salad ingredients in the mixing bowl, then gently toss everything together until evenly coated and the greens look vibrant and slightly glistening.
Plate the salad by arranging portions of the mixed greens, radishes, and tuna on individual serving plates, and finish with a final pinch of salt and pepper if desired.
