Preheat oven to 450 degree F. Place large baking sheet in oven to heat. Meanwhile, mix dill, orange peel, garlic and salt in medium bowl. Season with pepper. Combine tomatoes, oil and 1 teaspoon dill mixture in small bowl. Add chicken to remaining dill mixture in medium bowl and toss to coat. Cut 4 sheets of foil, each about 20 inches long. Place 1 foil sheet on work surface. Arrange 1 cup spinach on 1 half of foil. Place 1/4 of sliced chicken mixture atop spinach. Spoon 1/4 of tomato mixture atop chicken. Fold foil over, enclosing contents completely and crimping edges tightly to seal. Repeat with remaining 3 foil sheets, spinach, chicken mixture and tomato mixture, forming 4 packets total. Arrange foil packets in single layer on heated baking sheet. Reduce oven temperature to 400 degree F. Bake until chicken is just cooked through, about 10 minutes. Transfer to plates; let stand 5 minutes. Recipe by: Bon Apetit Posted to EAT-LF Digest by "lexi@ibm.net" on May 24, 1999,