Preheat oven to 180C.
Place the cauliflower on a baking tray lined with baking paper. Bake for 20 mins or until lightly browned. Set aside to cool for 10 mins.
Place the cauliflower in a large bowl with the mint, coriander and sunflower seeds. Combine the yoghurt, 2 teaspoons of water and curry powder in a small bowl. Pour over the cauliflower mixture and toss to combine.
Combine the beef and oil in a bowl and season well. Heat a barbecue grill or chargrill on medium. Cook the beef for 3 mins each side or until cooked to your liking. Transfer to a plate. Cover with foil and set aside for 5 mins to rest.
Serve the beef with the cauliflower salad and lemon wedges.