Preheat dutch oven to 350 degrees.

Combine oil, lemon juice, thyme and mix well.

Cut aluminum foil into squares as wide as the foil roll.
Place one chicken breast on a square.

Spoon 1/8 of the oil mixture on each breast.

Seal foil well and place in dutch oven.

Cover and bake 30 minutes.

Open foil and place one slice ham, cheese, and tomato on each breast. Bake with aluminum open and dutch oven covered for 5 minutes.