The word "cup" refers to the wine in the cup. Alternate translation: "The wine in this cup" or "This cup of wine" (See: [[rc://en/ta/man/translate/figs-metonymy]])
Here "blood, which is poured out" represents death. Jesus's death will establish the new covenant that God will make with his people. Alternate translation: "the new covenant that God will put into effect because I have shed my blood for you" (See: [[rc://en/ta/man/translate/figs-metonymy]])