Tomatoes and tuna were meant for each other, and fresh tarragon seals the deal. Soaking the onion in cold water tames the heat and sweetens its taste.
1/2 cup diced red onion
1/3 cup light mayonnaise
1/4 tsp. kosher salt, or to taste
Freshly ground pepper to taste
2 chunk light tuna in olive oil, drained
2 stalk celery, thinly sliced (about 1 cup)
1/4 cup packed coarsely chopped fresh tarragon leaves
8 cup torn lettuce or mixed greens
1 lb. small ripe tomatoes, cut into wedges
1 each lemon, cut into 8 wedges
Place onion in a small bowl and cover with cold water. Refrigerate for 20 minutes. Drain.
Whisk mayonnaise, salt and pepper in a medium bowl. Add tuna, celery, tarragon and the drained onion; stir to combine. Serve on a bed of lettuce (or mixed greens) with tomato and lemon wedges.
Cover and refrigerate for up to 1 day.