Boil water in a large pot. Add salt and tsp of oil. Add pasta into the boiling water and add whole tomato to blanch. Take out tomato after 5 mins .. continue to cook pasta.After 10-12 mins .. pasta would have cooked. Check .. take care not to overcook. It should be al dente ( Cooked just enough be to retain the shape ) . Drain and retain the stock water. Refresh the cooked pasta with running water. This avoids overcooking of spaghetti due to the heat .Cooked drained pasta is ready . Keep aside
Once blanched tomato has cooled .. peel off skin . Puree.
To begin with .. prepare a tempering ... splutter jeera in oil. Add onion, green chilli, ginger garlic paste. Saute till Onion turns translucent.
Add pureed tomatoes and add salt . Saute till oil separates.