I don't see why you couldn't use plain canned tomatoes instead. Personally, I wouldn't go to the trouble of stewing tomatoes. BUT, if you really want to stew your own, because they are good, a basic recipe would consist of first, removing the skin (cut an "x" on the bottom, blanch in boiling water for about 30 seconds, remove, place in bowl of ice water, and peel away skin when they have cooled off). These are recommended ingredients for say...2 lbs. of tomatoes:
2 Tbsp unsalted butter
2-4 teaspoons sugar (some people like them sweeter)
1/2 teaspoon salt
1/4 teaspoon freshly ground pepper
1 TBS finely minced onion
1 TBS finely minced green pepper
Cook slow on stove for about 30 minutes to 1 hour, or until juices are reduced.
This is just a very basic stewed tomato recipe and, like I said, I would be tempted just to use plain canned tomatoes in your recipe.
"Count yourself...you ain't so many" - quote from Buck's Daddy