To prepare the dressing, combine capers, shallot, lemon juice, honey, Dijon, salt and pepper in a small bowl. Gradually whisk in olive oil, taste and adjust seasoning if necessary. Set aside.
Prepare all salad ingredients. Place tuna on plate and salt and pepper both sides and brush with olive oil. Pre- heat the grill on high. Oil grates. When grill is hot, sear tuna on both sides for 3-5 minutes. Remove and set aside.
To assemble salad, on a platter or large serving bowl layer the outside of the platter with radicchio and lettuce leaves, then arrange all other ingredients around bowl. Slice tuna into 1/2 inch slices and arrange in the middle. Drizzle dressing over the top, sprinkle with chives and serve. Serves 4-6. Serve with pickled onions and radishes.