Heat butter in a pan, add onions and saute till translucent.
Add capsicums, tomatoes, mushrooms, salt and sugar and saute for three to four minutes.
Spread the butter on each bread slice than spread the pizza sauce on each bread slice and place the vegetable mixture over it.
Top up with grated cheese and place the slices on a hot tawa and cook till the cheese melts.
Cut into any shape and serve hot with tomato ketchup.