Lemon Chicken Tacos

1 lb. boneless, skinless chicken breasts, cut into 1/2-inch chunks
zest of 1 lemon plus 2 T. and 1 tsp. fresh lemon juice, divided
1 large onion, sliced
1 green onion, sliced
2 cloves minced garlic
2 tsp. olive oil
1/2 tsp ground cumin
1/2 tsp salt
1/4 tsp pepper
2 plum tomatoes, seeded and chopped
1/4 cup minced fresh cilantro
whole-wheat tortillas

Place chicken in plastic bag; add the zest of the lemon plus 2 tablespoons lemon juice. Seal bag and turn to coat. Refrigerate 1 to 2 hours. Saute onion and garlic in olive oil until tender. Add chicken, cumin, salt, and pepper. Cook and stir 4 minutes, or until chicken juices are clear. Remove from heat; stir in tomato, cilantro, and remaining lemon juice. Spoon onto tortillas. Top with lettuce and serve with salsa. 4 servings.