Spread insides or rolls with butter or margarine. For each sandwich, place 3 ounces sliced turkey over one half of roll.
Top with 1 slice each Monterey Jack and Cheddar cheeses.
Top with a layer of avocado slices and spoon 3 tablespoons of the Cilantro-Red Onion Relish over top. Add roll top.
Cut sandwich in half crosswise and serve, garnished with additional cilantro, if desired.
Cilantro-Red Onion Relish: Combine red onion, 1 cup chopped cilantro, salt, pepper and lime juice. Cover and let stand for 30 minutes to blend flavors. Store in refrigerator in an airtight container. Makes 2 1/3 cups.