Peel the onions. Bring a pot of salted water to a simmer, making sure there is enough liquid to immerse the whole onions. Add the onions and let them cook for 20 minutes. Remove the onions after 20 minutes, set aside, and let them cool.
Combine bulgur, quinoa, and couscous and spread evenly on the bottom of a large baking dish. Set aside.
In a saucepan, combine water, tomato sauce, and spices (curry, turmeric, anise, and cinnamon). Bring to a boil. Remove the star anise. Pour about 2/3 of the hot mixture over the grains in the baking dish, sprinkle a couple of pinches of salt and pepper, and mix to ensure that the grains are hydrated evenly. Reserve the rest of the tomato sauce mixture.
Preheat the oven to 375F (190C).
Cut off the bottom part of the onions just enough so that they stand straight. Cut off about 1/3 of the tops off and set them aside. Using a small knife, remove all but two outer layers. Reserve the removed flesh. Put the onions inside the baking dish on top of the grains and cover with the tops.
Wash the tomatoes. Cut off the top 1/3 of the tomatoes, and set the tops aside. Remove the insides of the tomatoes with a spoon. Reserve the removed flesh. Place the hollowed-out tomatoes inside the baking pan on top of the grains and cover with the tops.
Chop the reserved insides of the onions and place them in a small bowl. Repeat the same with the tomato flesh and place it in a separate bowl.
Heat one tablespoon of olive oil in a large frying pan over medium heat. Add the chopped onions, and cook for about 3 minutes or until light coloring appears. Next, add minced garlic and ground meat, 1/2 teaspoon salt, and 1/2 teaspoon pepper. Turn the heat to high and cook until the liquid evaporates, stirring frequently.
Add the remaining tomato sauce mixture and let the mix cook over medium heat for about 7 minutes.
Next, add the chopped tomatoes and continue cooking for 2-3 minutes over medium heat.
After that, add the broccoli and chopped parsley. Let simmer for 20 minutes, covering the pan three quaters of the way and stirring every now and again.
Taste and add more salt and pepper if needed.
Using a spoon, stuff the onions and tomatoes with the mix and cover with the tops. Drizzle with melted butter, sprinkle with a pinch of salt and pepper, and bake for 20 minutes.
If you want the tops to get a nice brown-dark brown color, place the baking dish under a broiler for about 2 minutes, constantly watching the vegetables.
Serve stuffed vegetables immediately, with pan-cooked grains on the side. Before serving, sprinkle some chopped parsley and drizzle with a bit of olive oil before serving.