1. Preheat oven to broil.
2. Heat oil for sautéing in a medium pot and add onion. Sauté onion until golden.
3. While the onion is sautéing, place grape tomatoes in a baking pan, spray with cooking spray, and toss to coat. Broil on the lower rack of your oven until they begin to shrivel and blacken slightly, about 25 minutes.
4. Add garlic to sautéed onion, stir, and continue to sauté an additional two minutes. Add water, both types of rice, and salt; bring to a boil. Lower heat, cover pot, and simmer 20–30 minutes, until rice is soft and water is absorbed.
5. Add basil and black pepper to taste. Add broiled tomatoes to pot and stir gently to combine. Serve warm.