|Blanched and seeded, ready to drain in the colander|
Bring a large pot of water to a boil. While you wait for it to boil, prepare a large bowl of ice water nearby.
Carefully drop the tomatoes into the pot of boiling water to blanch them for peeling - as many as will comfortably fit. After 1 minute, scoop them out with a slotted spoon and place them into the ice water. After a couple minutes, scoop them out of the ice water. Repeat with as many batches as you have.
Peel your blanched tomatoes. The skin should slip right off.
Once peeled, slice each tomato open. If you're using paste tomatoes, you can just scoop out the seeds and place seeded tomatoes in a colander over the sink or a large bowl. If you're using slices or the like, break them into a few pieces and squeeze carefully in your hand - do this over a bowl! You want all the seeds and much of the excess liquid to go into the bowl below while holding onto the tomato flesh. Once you're satisfied with the amount of seeds and liquid squeezed out, toss the flesh into the colander.
Let the seeded and squeezed tomatoes sit in the colander for a bit, shaking or stirring them a few times to encourage excess liquid to drain off. Once this is done, the tomatoes are ready to use or freeze. (I free them in quart freezer bags, about 3 cups per bag, pressed out kind of flat for tidy storage and faster thawing. You can thaw them in warm water.)