I made tomato paste for the first time this year because of limited freezer space and no space in the kitchen to can sauce. Timing wise, I did it over two evenings because the tomatoes needed to be processed and I still had work.
Cook down tomatoes like for sauce - I just cut the tops off, throw them in my largest pot with a little oil, salt and sugar and let them boil/simmer for three hours. Since the seeds and skin impart taste, I wanted to do this step too.
Run them through a food mill. Let cool out overnight and throw in the fridge before work the next morning.
Preheat
oven to 350, get two baking sheets and put the sauce on them. I did about a gallon of sauce onto both pans because they had a good lip. if you use an actual cake pan with a higher lip, it'll take longer.
Bake in the oven, mixing every 30 mins and switching the pans on the racks until
enough water has evaporated. Move it to one sheet and mix every 20 mins until brick red. Usually takes 3 to 4 hours.
Let cool overnight.
I then froze mine by plopping spoonfuls onto a parchment paper covered pan and then tossed them all into one plastic bag. They form together a little but because there's so little water, it's really easy to scrape the paste out with a
spoon or break chunks off.
I also did a quick test with stove top, I did a second batch with 1/4 of the sauce in the pot and 3/4 in the oven and they were cooked down in the same amount of time. It was the fastest and easiest way to cook down a ton of tomatoes with limited space and time. I think each batch was around 25 pounds. And the paste is delicious. It's really easy to throw in with some liquid and get a sauce.