Process peanuts, bouillon cubes, ginger, paprika, garlic powder, onion powder, black pepper, Nigerian red pepper, and 1 teaspoon salt in a food processor until finely ground, 30 to 45 seconds. Transfer 1 ½ tablespoons suya spice blend to a small bowl; set aside.
Pound steak using a meat mallet or rolling pin to ¼-inch thickness. Cut into 3- x 1-inch rectangles. Stir together Cameroon pepper, ½ cup oil, remaining 1 ½ cups suya spice blend, and remaining 1 tablespoon salt in a large, shallow bowl. Add steak pieces; stir until evenly coated. Cover and refrigerate at least 1 hour or up to 4 hours.
Preheat grill to medium (350°F to 400°F). Thread beef lengthwise onto skewers (about 3 pieces per skewer). Stir together 1 tablespoon reserved suya spice blend and remaining 2 tablespoons oil in a small bowl; set aside.
Lightly brush grill grates with oil. Place skewers on oiled grates. Grill, uncovered and undisturbed, until bottom sides are lightly charred, 1 to 2 minutes. Lightly brush skewers with oil mixture; flip and cook, undisturbed, until lightly charred and cooked through, 1 to 2 minutes. Brush skewers again with oil mixture, and transfer to a platter. Sprinkle skewers with remaining ½ tablespoon reserved suya spice blend. Serve with cucumber, tomato, and red onion.
