Heat large skillet over medium-high heat; spray with cooking spray. Add chicken, seasoning and 2 tablespoons water; cook 5 minutes or until browned, breaking up chicken with side of spoon. Transfer to large bowl; cool 5 minutes. Stir in cheeses; fold in tomatoes and onions. Makes about 2 ¼ cups.
Spread ¾ cup chicken mixture on 1 side of each tortilla; tightly roll up tortillas, tightly wrap in plastic wrap and refrigerate 30 minutes or overnight. Remove plastic wrap; cut roll-ups crosswise into 8 (¾-inch-thick) slices and garnish with onions, if desired. Makes 24 pinwheels.