Cut chicken into bite sized pieces and sprinkle with pepper. Saute in oil over medium heat until opaque, about 6 minutes. Drain. Cook broccoli until tender crisp; drain and arrange in bottom of a greased casserole dish. Place chicken on top. Mix together soup, mayonnaise and lemon juice, and pour over chicken. Sprinkle with cheddar cheese and bake, uncovered, at 350 degrees for 30 - 35 minutes.