Separate meat and vegetables into separate bowls. Mix together, the salt, pepper, cayenne, cumin, garlic, and onion powder. Season the meat liberally with the seasoning mixture. Toss to coat well. Season the vegetables with the remaining seasoning mix. Begin to build the skewers. Make them similar in size and with the same amount of ingredients. Grill over high heat turning occasionally until meat is cooked to desired doneness, and vegetables have softened slightly. Serve over a bed of white rice.