Wash and dry the meat. Melt 2/3 of the butter in a large pot. Add meat and brown on all sides. Add onions and sauté until they become golden in colour.
Add the tomatoes, tomato paste, salt, pepper and 1 cup of water. Cover pot and simmer until meat is tender, about 1 hour.
Remove the meat from the pot and keep it covered and warm. Strain the sauce and measure it. Add water if necessary until you have 8-9 cups of sauce. Pour the sauce into the pot and bring to a boil. Add rice. Cover and simmer until most of the liquid is absorbed, 20-30 min. Remove from heat. Add meat and mix well.
Sauté the remaining butter and pour it over the rice.
