Meanwhile, soak farro in water for 20 minutes. Drain and rinse. Cook farro in boiling water for 15 minutes until tender. Drain and cool.
Heat a heavy-based frying pan on a high heat. Cook prawns for 2 minutes, turning until cooked through.
In a screw-top jar, combine all the dressing ingredients and shake vigorously to combine.
Toss farro and kale with dressing in a large bowl. Add beetroot, prawns and feta. Sprinkle with sumac to serve.