Peel and finely chop the onions, dice the peppers and slice the mushrooms.
Heat the oil in a saucepan and gently fry the onion and garlic for 3-4 minutes until soft. Add the chicken, mushrooms and turmeric and continue to cook for a further 3-4 minutes; stir in the rice to coat in the oil.
Pour the hot vegetable stock over the rice in the pan. Bring to a gentle simmer; add the peas and cook, part covered, until the rice is tender (about 10 minutes).
To serve, stir in the chopped tomatoes, chopped parsley and lemon juice and pile onto a serving plate.