In a medium bowl mix all the filling ingredients. Taste for salt as sun-dried tomatoes vary greatly in saltiness. Set this filling aside, covered, for one hour for the bread crumbs to absorb the flavor.

Slice the fish into ¼-inch thick slices, 2 to 3 inches across. If they are longer cut them into 2 pieces. Between sheets of wax paper pound the fish gently with your fist to flatten them until they are ¹/₈-inch thick. When all the pieces are flattened, divide the filling evenly among them, placing it in the center of each piece. Fold the pieces in half covering the filling in a turnover fashion. (Ripiene can be prepared ahead to this point, covered with plastic wrap and refrigerated for up to 12 hours.)

Preheat a grill or broiler.

Brush the tuna packets with olive oil, sprinkle with salt and pepper and cook for a few minutes on each side until firm but still pink inside. Remove to a serving plate and serve at once, garnished with lemon slices.

Makes 12 servings.