Preheat oven to 350° F.
Peel tomatoes*; remove stem ends and scoop out seeds. Turn upside down on paper towel to drain.
Cook spinach according to package directions. Drain in colander. Squeeze moisture from spinach. Set aside.
Melt butter in a saucepan; add onion and cook until tender, about 5 minutes. Add spinach, seasonings and breadcrumbs; mix well. Add eggs and cook, stirring constantly, until well combined. Stuff tomatoes with spinach mixture; sprinkle cheese over top and dot with additional butter. Bake at 350º F for 10 minutes or until top is browned and tomatoes are thoroughly heated. Yield: 6 servings.
*To easily peel tomatoes, drop in boiling water for 1 minute.