Prepare the slow-roasted tomatoes. They can also be made in advance and stored in the fridge for several days, covered in olive oil.
Wash the tomatoes, place them on a baking sheet and drizzle generously with extra virgin olive oil. Sprinkle with salt and scatter the thinly sliced garlic over the tomatoes. Roast in the oven at 150°C for an hour, then turn off the oven and let the tomatoes inside until cold.
Spoon the tomatoes with their sauce in an airtight container or in a jar and store in fridge until ready to use them.
Cook the spaghetti in boiling salted water.
Meanwhile, heat the oil in a skillet over low heat with the garlic cut into thin slices and the crumbled chili pepper. When the garlic has softened and almost begins to melt, add the slow roasted tomatoes with some of their sauce.
Drain the spaghetti al dente, pour them into the pan, toss to season and serve with chopped parsley.