Preparing the tomato base for first tempering: In a pressure cooker,add 4 tomatoes slit into 4 pieces,garlic cloves ,ginger or grated ginger and water around 1/2 cup to avoid burning.Pressure cook this till 1 whistle on high flame.Then simmer the flame and cook for another whistle or for about 10 minutes.Let the steam release.Cool this mix and grind to a puree.Sieve the puree and keep aside.