Blend peanut butter, onion, garlic, lemon juice, soy sauce, brown sugar, hot pepper sauce and vegetable oil together (a blender does this well). Marinate pork in mixture for 10 minutes. Thread pork on skewers ( if using bamboo skewers, soak in water for 30 minutes to prevent burning). Grill or broil for 10-12 minutes, turning occasionally, until done. Serve with cooked rice, if desired.