In a saucepan heat oil over moderate heat until hot but not smoking and cook garlic, stirring, until golden, about 1 minute.
Add tomato paste, peanut butter, cayenne, and 1/4 cup broth and stir until smooth. Stir in remaining 3 3/4 cups broth and simmer, covered, stirring occasionally, 10 minutes.
Simmer soup, uncovered, 10 minutes, or until oil floats to the surface, and skim oil.