Vine-ripened umami

When the bones and whatnot are pretty much dark enough, I grab a can of tomato paste and thin it out a bit with water, and brush it on. If you're new here, I'll say it once more: it will not end up tasting like tomato at all. I'll roast it a bit longer, and the paste will get super dark. This is a place where it's possible to burn something, but even if you do, it's pretty fixable.

When the tomato paste is thinking about turning black, the oven gets a break. Throw everything in the stock pot and fill with COLD water. (Yes, it makes a difference.) If any of the onions seem too charred, toss 'em. You got what you needed from them during the roast. Then bring it up to a simmer slowly--almost even a sub-simmer. 200-205F is probably about right.

oh, and do smarter things than me: