If you haven’t already, cook the rice according to the package instructions and let it cool.
In a large bowl, combine the thawed corn, thawed peas, cherry tomatoes, drained tuna, chopped red onion, and cooked rice.
In a small bowl, whisk together olive oil, lemon juice, Dijon mustard, salt, and pepper to create the dressing.
Pour the dressing over the tuna and vegetable mixture. Gently toss until everything is well coated with the dressing. Place the salad in the refrigerator to chill for at least 30 minutes.
Once chilled, give the salad a final toss before serving.
