Tomato paste is considerably more difficult to make than you would think.
I'm a bit irritated at how many pounds of tomatoes I just wasted*.
But here's a tip- if the recipe says you can use a fine sieve instead of a food mill, IT'S A LIE.
*Well, not a total waste, I stuck them in the freezer. I'll toss them in a stew or something. Someday when the sight of them doesn't irritate me!