combine first 6 ingredients in a large saucepan; boil for 15-20 minutes. strain tomato mixture through a sieve, mashing tomatoes and onion withthe back of a spoon: discard pulp. return to to saucepan, and set aside. i use a food mill so much easier.
melt butter in a medium saucepan over low heat; add four, stirring until mixture is smooth. cook 1 minutes, stirring constantly. gradually add 1 quart scalded milk; cook over medium heat, stirring constantly till slightly thickened.
gradually stir milk into the tomato mixture, heat thoroughly. DO NOT BOIL!!! serve immediately. i froze it after it had cooled down.