Wash and chop tomatoes into chunks (if using fresh variety).
Place tomatoes and all other ingredients in a pot with a few tbsp of water.
Simmer till tomatoes are reduced to a pulp.
Put tomatoes through a sieve or in a blender to form a smooth puree.
Saute onions in pot.
Return puree to pot and add a tbsp or more of tomato paste.
:- This will improve the colour.
Add in a tbsp of butter and boil the sauce until it is thick and saucy.
Once cooled, add in chopped greens of your choice.
:- This sauce freezes very well. When tomatoes are plentiful and cheap, make a quantity and freeze in ice trays. Simply use the blocks as needed. With the addition of thyme, basil, fennel, mint, dhania etc. a variety of distinctive flavours can be obtained.