Bring about 3 quarts of water to a boil in a pot.

Meanwhile, heat the oil in a large saucepan. When it is hot, add the onions and 1 cup water; mix well and bring the mixture to a boil. Then reduce the heat to low, cover and cook for 10 minutes, until the water evaporates. Remove the lid and cook the onions for 5 minutes over high heat, stirring occasionally, until lightly browned.

Add the pasta to the boiling water and return the water to a boil, stirring the pasta occasionally at first so it doesn't stick together or to the pot. Cook the pasta for 12 minutes, or until firm to the bite (al dente).

Remove 3/4 cup of the pasta cooking liquid from the pot and reserve it.

Add the anchovies, garlic and oregano to the onions in the saucepan, mix well and stir in the salt, pepper and the reserved pasta cooking liquid.

Drain the pasta well and add it to the onion mixture. Toss to mix, then divide among 6 plates. Serve topped with the parmesan.