Sprinkle Southwest Seasoning on tuna. Heat oil in a large nonstick skillet over medium-high heat. Add tuna; cook 3 to 5 minutes on each side or until fish flakes with a fork.
Toss greens with desired amount of Cilantro-Lime Vinaigrette. Arrange greens on individual serving plates. Top with tuna, and drizzle with remaining vinaigrette.
I fix this all the time at our place at the beach during the summer. Instead of a salad, I just sear the tuna on the grill with Emeril's cajun seasoning and use the vinaigrette on top of it without the salad. My whole family loves it.