There were arias from three different Puccini operas played during the Luthor/Luckabee arc. I don't remember which episode the quote was from - I would guess Vixen...
1. Vixen - "Un Bel Di" from Madam Butterfly.
2. Shadows... - "Vissi d'arte" from Tosca.
3. Voices... - "Nessun Dorma" from Turandot.
Kathy