Preheat oven to 200°C. Line a baking tray with baking paper. Combine the kumara, onion, cumin, ground coriander and 1 tbs oil in a large bowl. Season with salt and pepper. Arrange in a single layer over the lined tray. Roast, turning occasionally, for 20 minutes or until golden brown and just tender. Set aside to cool slightly.
Meanwhile, combine the stock and quinoa in a large saucepan over high heat. Bring to the boil. Reduce heat to low; simmer, covered, for 10 minutes or until tender. Remove from heat. Set aside, covered, for 10 minutes.
Finely chop ¼ cup of the coriander. Place in a screw-top jar with the chilli, lemon juice and half the remaining oil. Shake until well combined. Season with salt and pepper.
Heat remaining oil in a large frying pan over high heat. Cook haloumi for 1-2 minutes each side or until golden brown. Transfer to a plate.
Combine the kumara mixture, quinoa, mint and remaining coriander in a large bowl. Arrange on a serving platter. Top with haloumi and drizzle with coriander dressing. Serve immediately sprinkled with lemon zest.