Clean, rinse and pet dry the chicken livers. Cut onions and bell pepper in thin strips (julienne) and saute in 3-4 tbsp cooking oil for a few minutes. Add a glass of water and cover with a lid. Cook for about 10 minutes, stirring from time to time.
Add the livers and tomato puree. Cook with the lid on for another 10-15 minutes, adding a little water if necessary.
Season with salt, pepper and thyme. Let them cook until the chicken livers are completely done (about 10 minutes more). One minute before turning off the heat add the crushed garlic and let it infuse into the sauce. Sprinkle with fresh parsley or dill. Serve on a bed of mashed potatoes or rice.