Sprinkle chicken with pepper and salt. Cut 4 pieces of heavy-duty foil, each large enough to enclose 1 breast half. Place chicken in center of each piece of foil. Divide cilantro in 4 equal parts; wrap 1 part around each breast half, covering as much of chicken as possible. Fold foil over chicken and place on baking sheet. Bake in 375F. oven about 45 minutes. While chicken is cooking, prepare Light Guacamole. Remove cilantro from chicken; reserve cilantro. Rewrap chicken to keep warm. To serve, place unwrapped chicken on serving platter and top with Light Guacamole. Garnish with chopped tomatoes.
Light guacamole: Place in cheesecloth over bowl, 1-cup non-fat plain yogurt. Drain 10 minutes; discard liquid. Peal 1 large avocado; halve and remove seed. Cut 1 half of avocado into chunks; reserve other half. In food processor container, place avocado chunks, 2 tablespoons chopped onion, 2 jalapeno peppers (seeded and finely minced), 1/2 teaspoon freshly ground pepper, 1/4 teaspoon salt, 1/4 teaspoon ground cumin, 2 teaspoons lime juice and drained yogurt. Add reserve cilantro from baked chicken to food processor container with avocado mixture; process until smooth. In medium serving bowl, place reserved half of avocado and coarsely mash with fork. Stir avocado mixture into mashed avocado.