Ingredients:

  Amount  Measure       Ingredient -- Preparation Method
--------  ------------  --------------------------------
   2      tablespoons   sour cream
     1/2  cup           packed fresh coriander
  10      cups          loosely packed mesclun
   1      cup           cherry tomatoes -- halved lengthwise
   1      cup           cooked fresh corn (cut from 2 ears)
   2      1" thick      tuna steaks
                        olive oil for brushing the tuna
                        nasturtium blossoms for garnish if
                        -- desired
                        ***FOR THE DRESSING***
   1      large         garlic clove -- minced and mashed
                        -- to a paste with 1/2 teaspoon salt
   2      tablespoons   red-wine vinegar
   1      tablespoon    fresh lemon juice plus additional to taste
     1/4  cup           finely chopped drained sun-dried tomatoes
                        -- packed in oil
   2                    plum tomatoes -- seeded and chopped
     1/2  cup           olive oil

Preparation:

Make the dressing: In a blender blend together the garlic, the vinegar, 1 tablespoon of the lemon juice, the sun-dried tomatoes, the plum tomatoes, and 1/4 cup water until the mixture is smooth and with the motor running add the oil in a stream. Add the sour cream, the coriander, the additional lemon juice, and salt and pepper to taste and blend the dressing until it is combined well. (The dressing may be made 1 day in advance and kept covered and chilled. Let the dressing return to room temperature.) In a large bowl toss the mesclun with the tomatoes and the corn and divide the mixture among 4 plates. Brush the tuna on both sides with the oil, season it with salt and pepper, and grill it on an oiled rack set about 4 inches over glowing coals for 4 to 5 minutes on each side for medium-rare, or until is cooked to the desired degree. Let the tuna stand for 3 minutes and cut it against the grain into 1/4-inch-thick slices. Divide the tuna slices among the salads and pour about 1/4 cup of the dressing over each serving. Serve any remaining dressing separately and garnish the salads with nasturtium blossoms.