I've got a quart of it; I was peeling tomatoes to freeze them and they
totally fell apart, so I juiced them. I added a big pinch of salt
(generous 1/4 tsp) and put it in the fridge.

I don't drink tomato juice.

So what's a good way to make tomato soup from it? Something like
Campbells, but more tomato-y and not so sweet. Here's what I have in
mind unless someone has a better idea:

Make a white roux. Add enough double-strength vegetable boullion (from
a cube) to make a thick paste. Whisk in the tomato juice, pepper, and
maybe some nutmeg. Adjust seasonings. Bring just to a boil, turn off
the heat, and add some heavy cream.

I think I left out onions, but not sure where to add them. Maybe cook
some grated onion in with the roux.

Bob