Boil spaghetti in salted water until tender; drain.
Melt butter in pan; saute onion and green pepper until soft.
Add tomatoes, salt, pepper. paprika, and sugar; simmer 10 minutes.
Add spaghetti; mix well.
Add 1/2 cup cheese.
Turn into greased baking pan. Sprinkle with remaining cheese.
Bake in 400oF oven until cheese is brown, 20 to 25 minutes.
As a variation this dish can be made by addding ground sausage meat or ham.