Tomato Gravy is a perfect accompaniment to meat loaf! The only question is: How are you going to cook the tomatoes before making them into gravy?
My mother used to can whole tomatoes at the end of summer. When she made meat loaf, she poured a jar of tomatoes over the raw meat loaf, squishing the tomatoes a little before putting it all in the oven. After the meat was cooked, she fished out the tomatoes, cooked them down in a skillet, and made them into gravy using milk & cornstarch. That's one option. And I'll show you another. =^..^=
The tomatoes have to be cooked down. If you're not going to put them in with the meatloaf, just cook them down in a skillet. Pour in the can of tomatoes & cut (or squish) them up. If you're using fresh tomatoes, peel & cut them into small pieces. You'll probably need to add a little water to get the fresh tomatoes started. Cook about 20 minutes or so on medium-low heat, stirring frequently.
If you cooked the tomatoes with the meat loaf, fish them out and put them in the skillet with a little water. Heat to boiling.
By this step, the tomatoes are cooked down, regardless of how you started them. Mom always added a little "juice" from the meat loaf pan to boost the flavor. That part is up to you.
Stir the heaping Tablespoon of cornstarch into the milk & mix well.
Add the cornstarch & milk mixture to the tomatoes in the skillet. Cook and stir until the tomato gravy thickens, just 2 or 3 minutes. Season with salt & pepper, as desired. If you want a smooth tomato gravy, use a hand blender. I've actually never fixed it that way, but I stand up for your right to do so.
Serve over meat loaf and mashed potatoes. =^..^=
CREAMED TOMATOES: Actually, it's all pretty much the same, EXCEPT do not add any meat loaf "juice" and don't thicken as much as a gravy. (If it's too thick, just thin out with a little milk.) Delicious on biscuits or boiled new potatoes. This is also great over macaroni & cheese!