Thinly slice the onion and peppers. Dice the tomatoes. Mince the garlic.
Heat the oil in a large frying pan or heavy-based casserole dish. Add the onion and gently sauté until transparent then adds the garlic and pepper strips. Put a lid on and gently cook for about 10 minutes.
When the pepper has softened add the tomatoes and cook for another 15 minutes (under cover) or until you get a stew. (Most Hungarians like lecso to be cooked into a mushy sauce – if you want this version, cook it longer, for 25-30 minutes).
Mix in the chopped parsley, season with ground pepper and serve.