Preheat an outdoor grill or grill pan to medium-high heat. Brush the grill grates with oil.
Season the steak lightly with salt and pepper. Grill, turning once, until the steak is charred on both sides, 3 to 4 minutes per side for medium rare. Remove to a cutting board and let rest for 10 minutes.
Cut the rested flank steak into small cubes (about 1/2 inch in diameter). Transfer to a bowl and add the red onion. Sprinkle with the Suya Spice Mix and drizzle with the olive oil. Toss well.
Pile the steak and onion on a serving platter and add the tomatoes and cucumber in a pile. Sprinkle with more Suya Spice Mix and serve with sliced baguette.
Suya Spice Mix:
Yield:about 1 scant cup
Put the peanuts in a blender or electric spice grinder and pulse until fine and powdery but not pasty. Add the ginger, cayenne, onion powder, garlic powder and salt as desired and blend just to combine. Transfer to an airtight container. The suya spice will keep for several weeks in a cool, dry place.
This can be served family style and eaten with your fingers or with toothpicks.