Melt butter in skillet and sauté onions until golden. Add chopped ham and sauté 1 minute. Divide mixture evenly among tomato cups. Place cups in a greased baking dish or individual ramekin dishes. Break 1 egg into each tomato. Bake at 350*F for 15 minutes or until firm to touch. Top with Hollandaise Sauce and serve immediately.
Mix egg yolks and lemon juice in the top of a double boiler. Over boiling water whisk in butter, one piece at a time. Continue cooking until sauce is thick.