If using bamboo skewers, soak them in water for 20 minutes before grilling. Heat a clean outdoor grill or grill pan to medium-high heat. If using metal skewers, no soaking is needed.
In a shallow bowl, stir together the ground peanuts, paprika, ginger, garlic powder, onion powder, salt, black pepper, and cayenne. Set aside 2 tablespoons of the seasoning blend for finishing the cooked skewers.
Pat the beef dry. Toss it with the oil in a large bowl, then add the remaining seasoning blend. Use clean hands or tongs to coat the beef evenly.
Thread the beef strips onto 8 to 10 skewers in a loose, wavy pattern. Do not pack the meat tightly; a little space helps it cook evenly.
Oil the grill grates lightly. Grill the skewers for 3 to 5 minutes per side, turning once, until browned at the edges and cooked to your preferred doneness. Thin beef strips cook quickly, so begin checking early.
Transfer the skewers to a clean platter and sprinkle with the reserved seasoning. Let rest for 3 minutes. Serve hot with sliced red onion and tomato, if desired.