Stir together mayonnaise, onion, lemon juice, lemon zest, salt and pepper until well combined. In separate bowl, toss Mann’s Rainbow Salad with tuna and sunflower seeds. Drizzle mayonnaise mixture over top; toss until evenly coated.
Divide salad evenly among 4 flour tortillas; Fold in one side and then fold up from the bottom, enclosing the filling. Fold in the other side of the tortilla and serve.
Tip: Salad mixture can be covered tightly and refrigerated.