Cook the spaghetti 2 minutes shorter than stated on the package. Pouring off.
Heat a little olive oil, cut the garlic into fine slices and roast in it. First deglaze with 2 cups of red wine, add the chilli flakes and zest, allow to reduce a little, add the very firm, pre-cooked spaghetti and stir everything carefully.
Let the wine evaporate, add a little more wine, let it evaporate again and so on until the spaghetti is cooked to the end and each has a glaze. Just before the end, season and add a tablespoon of butter and stir until they shine nicely all around.