Halve the peppers, remove the kernels, stems and white ribs and grill in the oven for 15 minutes (until the skin is black), remove and let rest for 5 minutes.
Then remove the skin and cut into thin strips.
Bring a large saucepan full of water to a boil.
Heat the oil in a large pan, fry the onions in it for 5 - 8 minutes until brown.
Add salt and pasta to the boiling water and cook until the pasta is al dente.
Meanwhile add the peppers to the onions and mix in. Add 3 tablespoons of the pasta water. Season with salt and pepper, stir in parsley.
Drain the pasta, then add to the pan with the vegetables.
Stir everything together and simmer for 3 - 4 minutes over medium heat.