Place the quinoa and water in a saucepan and bring to the boil. Reduce heat to low, cover with a tight fitting lid and cook for 15 minutes. Turn off the heat and stand for a further 10 minutes with the lid still on. Fluff quinoa with a fork and place in a serving bowl.
To make the rice, bring a saucepan of water to the boil, add 1 teaspoon of salt and the wild rice, bring mixture back to the boil, reduce heat to simmer and simmer rice for 30-35 minutes, or until tender. Drain and add to the quinoa.
Bring a saucepan of water to the boil, add 1 teaspoon of salt and the lentils, reduce heat to medium and cook at a rolling simmer for 20-25 minutes until the lentils are tender. Do not overcook or they will go mushy, so check them as you go. Drain the lentils completely, spreading on a paper towel if they hold any excess water. Place in the bowl with the quinoa and wild rice and dress with the lemon juice and macadamia oil. Season with salt and black pepper and add more lemon juice or oil, if desired, to taste. Stir through tarragon.
Preheat oven to 180°C. Place macadamias on a tray and sprinkle with the cumin and ½ teaspoon of salt. Roast for 10 minutes, until golden. Meanwhile, heat oil in a heavy based frying pan over high heat. Add onions and cook over high heat for 2-3 minutes so they turn golden, reduce heat and cook for 5 more minutes, until tender. Stir through the salad with the roasted macadamias and serve immediately.