Grill tuna steaks as you like them, and set aside.
Divide the salad greens between 4 dinner plates, and top with the tuna steaks. Top with onion slices and melon balls, and drizzle with Curry Vinaigrette and garnish with lime wedges. This salad is great with the tuna hot off the grill or with the tuna grilled in advance and chilled.
In a small bowl, mix the curry powder, honey, lime juice and vinegar together with a whisk. Slowly whisk in the olive oil and canola oil to emulsify and taste and adjust the flavors accordingly. Store in the refrigerator until ready to use. For a variation, try adding ΒΌ cup fresh mango juice in place of the lime juice.