In the top of a double boiler, whisk egg yolks and lemon juice together. Add 1/3 of the butter, about 3 tablespoons. Place double boiler over simmering water. Cook, beating constantly, until butter melts and sauce begins to thicken. Add 3 more tablespoons of butter, stir until butter melts, then add remaining 2 tablespoons of butter. Slowly whisk in boiling water. Continue cooking over simmering water, stirring, until mixture thickens, about 2 to 3 minutes. Remove from heat; stir in salt and cayenne pepper. Place ham slices and tomato halves on rack of broiler pan. Broil until ham begins to get browned and tomatoes are cooked through. While ham is broiling, pour about 2 inches of water into a large skillet. Lightly salt water; bring to the boiling point. Carefully put eggs in water, breaking into a cup first, then gently slipping them into the water one at a time. Simmer eggs for 3 to 5 minutes or until set. Remove with slotted spoon. Drain. On serving plates, place English muffins, 2 halves to each plate. Top halves with 2 slices of ham and a poached egg. Spoon a little sauce over the egg and place a thick slice of boiled tomato next to the egg. Serve.