Boil spaghetti in slightly salted water 11 minutes or as indicated on the package. Keep 2-4 tbsp of cooking water. Put aside.
Heat 2 tbsp of olive oil in a large pan. Add the washed and cleaned clams. Cook (covered), shaking the pan occasionally for 7 minutes or until the clams open. Remove any clams that do not open.
Take a small bowl, place a strainer with a piece of light white cloth over it , pour the sauce left in the pan and filter thoroughly.
Again heat 4 tbsp of olive oil in a pan. Add chopped garlic and tomatoes; cook over medium heat 5 minutes. Add lemon juice and 1 tsp of lemon rind, pour the sauce previously filtered. Cook another 2 minutes.
Add to the pan the shelled clams, the whole ones, chopped red chili. Rapidly mix and turn off the heat after a couple of minutes.
Immediately add spaghetti to the pan with the clams, pour 2-4 tbsp of cooking water and mix everything quickly. Garnish with fresh parsley.