2 cups dried white basmati rice
1/2 cup vegetable oil or ghee
2 medium onions, thinly sliced
1 pound potatoes, peeled and cut into 3/4-inch cubes
4 tablespoons black cumin seeds (see headnote)
2 to 3 teaspoons fine sea salt
2 teaspoons ground turmeric or 1/2 teaspoon ground saffron
4 cups no-salt-added chicken broth, or water