Preheat the oven to 375 degrees. In a large enameled cast-iron casserole, heat the oil; add the onion and saffron. Cook, stirring, over medium heat, about 5 minutes, until onion is softened but not browned. Add the rice and stir until coated with oil. Add stock and bring to a boil over high heat. Simmer 2 minutes, stirring occasionally. Cover the casserole, transfer to the oven and bake 15 minutes.
Remove from the oven and let stand, covered, up to 30 minutes. Fluff with a fork and let cool. Using a small funnel, press cooled rice into a cone shape and set out in rows on a tray or cookie sheet. Serve with Pineapple-Pepper Lava (recipe follows) spooned on top, or let guests spoon their own.
Makes 10 to 12 servings