Complex sentence: In Neapolitan cuisine and other similar cuisines in southern Italy, the frittata may contain pasta, such as spaghetti or macaroni; traditionally, this was pasta left over from a previous meal, including its original sauce (e.g. tomato sauce) on it.
Split into simpler sentences: In Neapolitan cuisine and other similar cuisines in southern Italy, the frittata often contains spaghetti, macaroni, or another kind of pasta. Usually this pasta is left over from a previous meal and has sauce (e.g. tomato sauce) on it.