Eggless Egg Salad Sandwiches

1 cup liquid egg substitute
1/4 cup chopped celery
1/4 chopped onion
2 tablespoons fat-free mayonnaise
12 slices whole wheat bread
6 lettuce leaves
1 large tomato, cut into 6 thin slices

1. Pour egg substitute into an 8-inch nonstick skillet; cover tightly and cook over very low heat for 10 minutes. Remove from heat and let stand, covered, 10 minutes. Cool completely.
2. Dice egg and place in a small bowl. Add celery, onion and mayonnaise; mix well. On each of 6 bread slices, place a lettuce leaf and a tomato slice; top each with 2 to 4 tablespoons egg salad and finish with a remaining bread slice.