One of my final tomato preserving projects of the season was to make tomato paste. I started with 10+ pounds of Blue Beech paste tomatoes.
The tomatoes were washed, cut in half lengthwise, and layered cut side up in my largest roasting pan. Those got baked in a 300F oven for about 2 hours, cooled, and then pureed with a food mill. The puree was then simmered on the lowest flame that my stove can produce for a few hours. I stirred it every so often. Once the puree was reduced by about a third I ladled it into shallow trays that fit on the racks of my dehydrator. At this point the puree still weeps a watery juice.
It took a few hours to reduce down to a very thick paste. The edges of the puree dry more quickly and can get leathery so I stir the puree a few times during the drying process.
The final result is a very thick paste that doesn't weep any watery juice at all. I like to stir the paste together in a bowl and chill it before packing it into containers for the freezer.
The final result was 27 ounces, 5 ounces per container and one little 2 ounce log rolled in plastic wrap. The paste has such a high sugar content that it doesn't freeze as hard as a rock. I can usually pop it out of the container while frozen and cut off chunks without thawing the entire contents.