In a non-reactive skillet, sauté the bacon in 3 tablespoons of olive oil until lightly browned. Add the onions and cook, stirring, over medium heat until golden. Add the crushed peperoncini, tomatoes, salt and simmer for 10 minutes. While the sauce is simmering, cook the capellini in 4 quarts of salted boiling water until al dente, about 3 minutes. Drain the pasta and toss with the remaining olive oil. Stir in the sauce, add the cheese, toss well, and serve immediately. (This is the only exception in tossing pasta with olive oil before adding the sauce. The capellini are so thin that the coating of oil limits their absorption of the hot sauce and helps to keep them al dente for a longer period while eating them.)