Place the tomatoes in a medium pot of boiling water for about 30 seconds, this will make it easy to remove their skins. Remove the tomatoes from the pot, let cool a little, peel off the skins and discard. Slice the tomatoes in half, scoop out all of the seeds and discard them. Finely cube the tomatoes.
Mix in the chopped tomatoes and tomato paste, cover, and let stew for another 10 minutes. Add the summer squash/zucchini and another pinch of salt, cover, and let stew for 30 minutes, mixing periodically. The squash should release enough water, but if the pan gets too dry, add a small splash of water to get things going.
Mash the vegetables with a potato masher right in the pan, until mostly smooth with some chunks throughout. Mix in the sugar. Cover and let stew for another 10 minutes. Remove the lid, turn the heat up to medium, and let any remaining water cook off, stirring periodically. This should take 10-20 minutes. Taste for salt and adjust if needed. Let cool, transfer the caviar to an air-tight container and keep refrigerated.
Recipe by Golubka Kitchen at https://golubkakitchen.com/summer-squash-caviar/