Heat butter in a pressure cooker.
Add onions, cloves, cinnamon and pepper.
Saute till onions become brown in colour.
Add chopped tomatoes. Keep frying in low flame until the tomatoes are mushy. Take care and do not burn the tomatoes.
Add 6 cups of water and pressure cook for 2 whistles. Cool down and remove the cinnamon piece.
Grind the tomatoes and strain it.
Heat the soup. Stir ocassionally.
Add the corn flour which has been dissolved in 1/2 cup water to the soup so as to thicken it.
Add salt, freshly ground pepper powder and sugar and cook for 5 - 6 mins. As an option you can also garnish the soup by spluttering some curry leaves and a red chilly in little ghee for those who prefer so.