Preheat a fan-forced oven between 180°C and 220°C (356°F to 428°F). Line a baking tray with parchment paper and place the whole red bell peppers on top. Roast for approximately 40 minutes, then turn the peppers and cook the other side for another 10 minutes. Do not discard any of the juices released by the peppers.
Remove the roasted peppers from the oven and allow them to cool at room temperature. If you are short on time, briefly place them in cool water until they are comfortable to handle.
Carefully collect the flavorful pepper juices from the baking tray and pour them into a blender.
Remove the stems, peel away the skins and discard most of the seeds. Place the roasted pepper flesh directly into the blender. A few remaining seeds are perfectly fine. Pour in any additional juices released while peeling the peppers.
Blend the roasted peppers for 20 to 30 seconds, or until the sauce is smooth. Set aside.
Bring a large pot of water to a boil and add one tbsp of rock salt. Add the spaghetti alla chitarra and cook it for 8-12 minutes or according to the packet instructions. Gently push the pasta into the water and stir it at least twice during the first two to three minutes to prevent it from sticking.
While the pasta cooks, place a large frying pan over medium-low heat and add a generous amount of EVOO. Add the crushed garlic and cook gently for approx. 30 seconds.
Pour the blended red pepper sauce into the pan and stir well so it absorbs the garlic and EVOO. Add a generous amount of chopped parsley, mix and simmer gently for 5 to 10 minutes. Remove pan from the stove.
Once the spaghetti is al dente, transfer it directly to the frying pan using tongs. Mix thoroughly until every strand is coated in the silky red sauce, then give it a confident toss.