Cut core from tomatoes and remove pulp. Invert tomatoes on paper towels and drain for 30-45 minutes. Coarsely grate unpeeled zucchini and place in boiling water for 2-3 minutes. Immediately pour zucchini into colander and rinse with cold water. Let zucchini drain for 30 minutes. Preheat oven to 300°. Mix the drained zucchini with pesto and stuff into tomatoes. Place in lightly greased baking dish and sprinkle with grated cheese. Bake for 30-40 minutes, or until heated through. 8 servings.