Ketchup. Not tomato sauce.
I can’t choose, we like both. I do my pot roasts in a crock pot and make tons of gravy from the awesome juices. Once cooled, I save a quart freezer bag that subsequently gets pulled out to accompany meatloaf. If I don’t have any gravy reserves, we do the tomato-y glaze instead.
Brown gravy for me. That’s how my mom made it, and meat loaf is one of the few things I can actually make on my own (I fail as a cook). We usually use mushroom gravy, with extra ones tossed in because we both like mushrooms.
I voted for the gravy, but don’t really care for either.
The best thing to do for meatloaf is to bake it on a flat pan, preferably on a rack, so it doesn’t turn into a soggy greasy mess.
The second best thing is to use good-quality pork sausage (homemade if possible) to make up half the quantity of meat.
Between the two, it’s definitely brown gravy! Yum! I do not like the baked on tomatoey stuff at all.
We don’t usually have either at home. We just cook it and then dip the bites in a bit of ketchup as we’re eating it.
I think the whole point for me is that meatloaf is sort of bland. That is: it tastes like meat and sauce. It’s comfort food! That said, my basic meatloaf recipe is similar to Quakers: meat, oats, egg. Sauce is ketchup, yellow mustard and brown sugar mixed. And now I want meatloaf. Guess I know what’s for dinner!
Gravy for hot meatloaf, with mashed potatoes.
Ketchup for cold leftover meatloaf sandwiches.
I top mine with bacon strips and glaze with ketchup.
My goofy SIL puts boiled eggs inside, lined up in a row so every slice has an egg slice in the middle of it. WTF? Meatloaf Surprise? No sauce. And no flavor.
Last night I was reading about the Stanley Hotel in Estes Park, CO and their specialty of the house is elk, buffalo and pork meatloaf with a mushroom gravy for $22. a plate. Yum.
Ketchup-based sauce, glazed on, with more liquid after it’s sliced.
Sadly, I don’t have the recipe for my favorite meatloaf. And even if I did, I’d have to adjust it a good deal, since the original recipe was for about 200 servings.
Tomato-based barbecue sauce.
I used crushed matzah as the bread in my meat loaf. Because, you know, leaven can wait.
I have never had less trouble choosing on a poll; like French fries, meatloaf exists solely as a vehicle for ketchup. It’s not that brown gravy is bad on meatloaf. It’s simply unimaginable, and that liter of ketchup I bought tonight isn’t going to eat itself.
My favorite tomato-based glaze is just plain ketchup mixed with an equal amount of Muscovado real brown sugar. Spread it all over the top and sides while the meat loaf is in the oven and then spoon on as needed when dining.
Gravy on mashed potatoes? Ewww. Give me butter any day.
I thought Meat Loaf existed solely as a vehicle for Jim Steinman.
Both should have been an option.
Proper meat loaf gets a tomato based glaze baked into the top while in the oven. Then when sliced and plated next to the mashed potatoes, gets brown gravy over the top.
BBQ sauce. I make a turkey, couscous, and veggie meatloaf with barbeque sauce.
Wow. I never imagined one food could be wrong in so many ways! 
Can’t make gravy, eh? 
I honestly prefer it plain, although the red sauce doesn’t hurt that. Ketchup would, though. The sauce can’t be that strong. You can make the red sauce with ketchup, but that can’t be all that’s in it.
I voted for gravy, though, based on the fact that, if you think need to put stuff on it, it’s probably not very moist, and gravy is better for moistening. But I’d still rather have a moist one with no sauce.