Heat the oil in a medium saucepan over medium heat. Cook the garlic until fragrant, 1 minute.
Add the tomatoes (and their juices), tomato paste, peanut butter, broth, vinegar, cayenne, and 1 teaspoon salt. Whisk to combine. Bring to a boil.
Add the rice, reduce heat to low, cover, and cook until the rice is tender, 15 to 20 minutes.
Ladle the soup into bowls and garnish with the scallions and peanuts.