For the roasted red pepper sauce, in blender combine salad dressing and half of the roasted red sweet peppers; process until nearly smooth.
For tuna filling, chop remaining peppers. In a bowl combine chopped peppers with tuna, corn, and 1/4 cup of the roasted red pepper sauce.
For each club sandwich, spread two slices of toasted bread with tuna filling, top with lettuce leaves, stack the two slices, then top with a third slice of toast. Cut in half diagonally. Serve with remaining roasted red pepper sauce.