Heat the olive oil in a large skillet over medium heat. Stir in the onions, sprinkle them lightly with salt and cook, stirring, until wilted, about 3 minutes. Crumble the sausage into the skillet and stir until it is has rendered most of its fat and is golden brown, 5 to 7 minutes. (If the sausage has given off some water, allow time for the water to boil away before the sausage begins to brown.)

Drain the excess fat from the skillet. Add the tomatoes, cherry peppers and oregano and bring to a boil. Lower the heat so the sauce is at a lively simmer and season the sauce lightly with salt. Cooking, stirring occasionally, until the sauce is thickened, about 20 minutes.

Meanwhile, Bring 6 quarts of salted water to a boil in an 8-quart pot over high heat. Stir the gemelli into the boiling water. Return to a boil, stirring frequently. Cook the pasta, semi-covered, stirring occasionally, until done, 8 to 10 minutes.

If the skillet is large enough to accommodate the sauce and pasta, fish the pasta out of the boiling water with a large wire skimmer and drop it directly into sauce in the skillet. If not, drain the pasta, return it to the pot and pour in the sauce. Bring the sauce and pasta to a boil, stirring the pasta gently to coat with sauce. Check the seasoning, adding salt if necessary. Remove from the heat and add half the grated cheese. Toss well, then transfer to a warm serving platter or individual bowls. Top with the remaining cheese, and serve immediately.