We call them Scalloped Tomatoes in the South. Basically, you cut bread into cubes, saute them in butter until brown and crisp along with some finely diced onion. Add this to some good canned (home canned is best) tomatoes or peeled and chopped fresh tomatoes. Add a good amount of brown sugar and salt and pepper to taste. Bake in a moderate oven until brown and bubbly.

Here is a similar recipe, but use cubed bread, not crumbs:

Scalloped Tomatoes

1 large (28 ounces) can tomatoes, cut up
1/4 cup chopped onion
1/4 cup butter
1 1/4 cup fine dry bread crumbs
1/2 cup brown sugar
1 teaspoon salt
1/8 teaspoon pepper

Saute the onion in butter. Add the bread crumbs and brown sugar. Cook the mixture slowly until hot and well blended. Add the tomatoes and seasonings. Place the tomato mixture in a shallow buttered baking dish. Bake 45 minutes at 350°.
Serves 6 to 8.

I don't care for stewed tomatoes but your grandmother is about the same age as my mother would be & this was the one my aunt used:
STEWED TOMATOES
6 tomatoes, fresh or canned
2 TBL butter
Salt & pepper
Crumbs

Pour boiling water on fresh tomatoes & after they have remained covered one minute drain them & plunge them into cold water. Slip off the skins, remove the hard stem ends & cut the tomatoes in pieces. Stew them in their own juice in a graniteware or porcelain-lined kettle (old recipe) until tender, add butter, salt & pepper. Bread crumbs or cracker crums blended with the butter may be added for thickening.~~

This recipe was passed down from grandma to mom to me. We use fresh tomatoes (we grow our own during the summer). We make up lots of batches and freeze it in freezer bags. It goes great over scrambled eggs for breakfast or toast. It's delicious!

Grandma Fern's Stewed Tomatoes
3 slices bacon
1 green pepper-chopped
1 onion-chopped
7or8 tomatoes-chopped
2 TBS sugar
salt and pepper
Seasoned bread crumbs

Fry bacon till crispy in pan. Remove and crumble on paper towels. Drain off all but 2 TBS bacon grease. In grease fry pepper and onion till translucent. Add tomatoes, S&P, and sugar. Cook till heated through and tomatoes start to break down. Add crumbled bacon and bread crumbs stir. Enjoy!
NancyLouise

My ex-MIL used to just heat a can of tomatoes, some torn up stale bread and a little sugar.

Sorry, no recipe, I never liked it. :+)