This was not a dish my grandmother Angelina ever made, as far as I know, but it is certainly the kind of pasta-cum-vegetable dish that formed the foundation of her culinary repertoire. You saute sliced red onions in a generous amount of olive oil in a wide skillet or braiser. When the onions have softened and become translucent, add anchovy filets to taste (I like a lot) and finely chopped parsley and cook for a few more minutes, just until the anchovies have melted into the oil. Season to taste with salt and pepper. (You should not need too much salt, given the anchovies.) Cook the spaghetti al dente and, when they're done, drain (but not too well, you'll want some of the water to cling to the pasta to help moisten the dish) and turn them into the skillet with the onion and anchovy sauce. Mix well, adding some of the pasta water if it's still too dry--the pasta should 'flow' nicely as you toss it. Serve immediately, with some more chopped parsley and un filo d'olio on top.
NOTES: The robust flavor and texture of the onion and anchovy sauce would go well with other long pasta shapes like linguine or even bucatini. The original recipe (which you can find here) called for ricotta salata grated on top, but the idea didn't appeal to me. But try it if you like.
A tip on slicing onions: for some reason, it makes a big difference if you slice an onion lengthwise or across. When you want to onion slices to retain their individuality--and that's what I wanted to for this dish--slice them lengthwise. If you want to onion for its flavor only, slice them thinly across the grain, and they will 'melt' into whatever sauce you're making.
