Wash the quinoa in plenty of cold water and drain. Put in a pan with 250ml (1 cup) of water. Bring to the boil and then reduce the heat, cover the pan and simmer for 10-12 minutes until all the water has been absorbed.
Preheat the oven to 180°C. Sprinkle the chicken breast with paprika seasoning. Heat a non-stick frying pan and add the chicken to the dry pan. Cook for 2 minutes to sear, then turn over and sear the other side. Transfer the chicken to a paper-lined baking tray and bake for 12 minutes.
Put the mustard seed oil in a saucepan over low heat. Add the mustard seeds. Add the onion and fry for 5 minutes, until lightly golden. Add the mushrooms, stock and cook until the stock has reduced by half.
Add the apple juice and cook for 15 minutes until reduced by half. Add the vinegar, season with salt and pepper and stir in quinoa.
Toss together the tomatoes, parsley, lemon zest and juice. Serve the quinoa topped with the chicken and the tomato salad.
