In a medium saucepan, over medium heat, heat the oil and garlic for 1 minute. Add the tomatoes, tomato paste, peanut butter, broth, vinegar, cayenne, and salt and whisk to combine. Bring to a boil. Add the rice, reduce heat to low, cover, and cook for 20 minutes. Ladle into individual bowls and garnish with the scallions and peanuts.
Tip: For a more substantial soup, add an additional spoonful of cooked rice to the bowl with the scallions and peanuts.