Bring 2 quarts water to a boil in a large saucepan. Add salt and beans. Allow beans to re-hydrate by boiling for 15 minutes, skimming off "scum" from surface of water, and allowing it to sit, covered, for 1 hour.
Heat oil in a separate pot, and saute onion until it begins to turn translucent. Add 6 cups of water to this pot, and then add rice, allowing to simmer until water is absorbed and rice is soft, about 20 minutes. Stir okra into pot of rice to warm okra. Gently mix rice and okra with beans and tomatoes in a bowl and serve.