Thanks to everyone for your suggestions!
I am trying to come up with something that uses the tomato powder, and that doesn't involve going through dehydrating the complete sauce and then breaking it down small enough to rehydrate easily. Partly because we have 19 people worth of this to make, and partly because running it through the blender after dehydrating takes the texture out of the sauce. I tried a couple of mixes with the tomato powder and herbs, vegetables, etc. The first thing that became apparent was that with just those ingredients, it comes out too thin, but with less water the flavor is way too strong. Even adding some instant mashed potatoes to thicken it, it didn't taste right.
I did some more poking around on the web, and found these:
Vegetarian Spaghetti Sauce
1 packet dry spaghetti sauce mix (see below)
3/4 cup tomato powder
1 cup TVP (I'm using hamburger gravel for the omnivores)
2 tablespoons minced dried onions (home dehydrated)
2 tablespoons julienned sun-dried tomatoes
1 tablespoon dried sliced mushrooms (home dehydrated)
1 2.25-ounce can sliced olives (I am not taking cans on the trail. Chopping up the drained contents of a regular big can of olives and dehydrating that seems to work.)
1 tablespoon olive oil
1 pound pasta
At home, combine the spaghetti sauce mix, tomato powder, and TVP in a small plastic bag, In a second bag, combine dried onions, tomatoes, and mushrooms. (Tried putting a small test batch of everything into one bag, and found the moisture in the sun-dried tomatoes makes the tomato powder clump all up, so 2 bags it is.)
In camp, pour contents of spaghetti sauce bag into a pot and gradually stir in 4 cups water. Add dried vegetables. Bring to boil, reduce heat, and add olives and olive oil. Simmer 10 to 15 minutes, and serve over pasta. (I found bringing it to a boil and then turning off the stove and letting it sit for 15 minutes produced about the same result as simmering it.) Serves 4. (So for 19 on the trail I am making 5x of this.)
Spaghetti Sauce Mix
This makes 4 batches of spaghetti that serve 4-6 people each, so one recipe of this mix should be enough for 5x the recipe above.
1/4 cup instant minced onion (I used granules from bulk jars at my food coop)
1/4 dried parsley flakes (could have dehydrated myself but it was too easy to get from the bulk jar at the coop)
1/4 cup cornstarch
1 tablespoon dried green pepper flakes (I had some Harmony House already)
1 tablespoon salt
1 teaspoon minced garlic (coop bulk jars)
1/2 teaspoon white pepper
1 tablespoon sugar
1 tablespoon dried Italian seasoning (I was working out what that would contain, probably basil, oregano, marjoram, maybe fennel? but then found it in bulk at the coop.)
Combine all ingredients in a small bowl and blend well with a wire whisk. Spool mixture into a tightly closed container and store in a cool, dry place. Use mix within 6 months.
I treated each 1/5 of this (about 1/3 cup) as 1 packet in the spaghetti recipe above.
Like I said, it comes out a little thin, but probably folks won't mind, or maybe I'll put in a bit more cornstarch. Only so much time left for experimenting, though.
And yes, I have FBC which has a *lot* of very handy recipes but not any particular guidance on using tomato powder.
Once again, thanks to all!