Place rice and water in a large saucepan and bring to a boil. Cover, and reduce heat to low. Simmer until rice is tender and water has absorbed, about 30 minutes.
Heat olive oil in a large saucepan over medium-low heat. Add onion, and cook until soft and golden, stirring frequently. Add garlic and ginger, and cook until fragrant, about 5 minutes. Stir in tomatoes, and season with cayenne pepper. Increase heat to medium, and bring to a gentle simmer. Stir in peanut butter and heat through. The mixture will thicken. Serve over rice.
