In a small bowl or ramekin, add the finely chopped shallot and cover with white wine vinegar and 1/2 teaspoon of sugar.Set aside and let marinate while preparing the tuna.
Drain the tuna removing any excess water.In a bowl, add the tuna and with a fork; break into bite size pieces.
Add the remaining ingredients and mix well.
Serve on a bed of mixed salad, tossed with olive oil and red balsamic vinaigrette. The ratio for the vinaigrette is 1 part vinegar to 3 parts oil.