1. Combine first 7 ingredients in a large bowl; add 1 teaspoon oil, 1/4 teaspoon salt, and 1/8 teaspoon pepper, tossing to combine.
2. Heat a large heavy grill pan over medium-high heat. Rub remaining 2 teaspoons olive oil over tuna; sprinkle tuna evenly with remaining 1/4 teaspoon salt and 1/4 teaspoon pepper. Coat pan with cooking spray. Add tuna to pan; cook 3 minutes on each side or until desired degree of doneness. Arrange 1 1/2 cups salad on each of 4 plates; top each serving with 2 tuna steaks. Serve with lime wedges, if desired.
MyRecipes is working with Let's Move!, the Partnership for a Healthier America, and USDA's MyPlate to give anyone looking for healthier options access to a trove of recipes that will help them create healthy, tasty plates. For more information about creating a healthy plate, visit www.choosemyplate.gov.