Heat the oil in a large, heavy kettle or saucepan over medium heat. When the oil is hot but not smoking, add the meat and brown it well on all sides, which will take about 9 minutes. Add the onions, stir so they are coated with oil, and cook until they are deep golden, about 10 minutes, then crumble the saffron over the mixture. Season it with the salt, stir, and 1 cup (250ml) of the hot water. Stir and cook for 4 to 5 minutes, to blend the ingredients and allow the saffron to soften. Add the tomato paste and the 2 quarts (2 liters) of hot water, bring to a boil, cover, and reduce the heat so the liquid is simmering merrily. Cook until the meat begins to turn tender, about 30 minutes.