Finely chop the onion and garlic. Dice the mushrooms and green pepper.
Heat the oil, then gently sauté the onion and garlic. Add the mushroom and pepper pieces and stir for 5 minutes or so until the liquid evaporates.
Add the spices and stir for 30 seconds then add the tomatoes purée and chopped tomatoes. Stir for 3-4 minutes until the tomatoes are tender. Add the lemons juice and season with salt and pepper. Stir for another 10 seconds or so, then fold in the herbs.
Serve immediately or let it cool and chill.