Tuna Coleslaw with Grapes

Juicy red and green grapes, julienned vegetables, and bits of tuna tossed in a sour-cream dressing make a wonderfully crunchy, sweet-tasting salad. Spoon the salad over baby greens and garnish each plate with small clusters of grapes. For convenience, you may use the prepared broccoli slaw available in plastic bags from the supermarket in the salad section. It should contain shredded broccoli stems, purple cabbage, and carrots. If broccoli slaw is unavailable, substitute the classic coleslaw mix: cabbage, carrots, and red cabbage.

Mixed baby salad greens (mesclun)
1 can (about 6 ounces) solid or chunk light tuna packed in oil, well drained and broken into large chunks
1 1/2 cups red and green seedless grapes, halved crosswise, plus small grape clusters for garnish
1/4 cup diced red onion
1/4 cup diced celery heart
Grated zest of 2 limes, plus extra for garnish
1 teaspoon fresh lime juice
1/4 teaspoon salt
Freshly ground black pepper
3 tablespoons mayonnaise
2 tablespoons sour cream
1 cup combination of shredded mixed broccoli stems, carrots, and red cabbage