In a medium saucepan heat oil over medium-high heat, add onions and garlic and saute until soft. Add cumin and cook 1 minute. Add rice and coat with the oil. Add reserved cooking liquid, season with salt and pepper and bring to a boil. Reduce heat to a simmer, cover pot and cook for 12 to 15 minutes. Remove from the heat, fluff with a fork and fold in the cooked black beans, green onion and jalapeno. Season with salt and pepper to taste. Serve at room temperature.