What is the best move for Black? [FEN ""]
[startply "25"]

1. e4 e5 2. Bc4 Nc6 3. Nf3 Nf6 4. Nc3 d6 5. h3 Be7 6. d4 exd4 7. Nxd4 Bd7 8. O-O O-O 9. Bg5 h6 10. Bxf6 Bxf6 11. Nxc6 Bxc6 12. Re1 Re8 13. Qf3


What is the best move for Black here, and why?
As stated in my comment, I don't think this is a puzzle because there is no clear decisive tactical sequences.

A good move would be 13...Qe7, putting pressure on the e4 pawn and prepare for ...Bxc3. If White did nothing, Black could then continue with ...Be5 and ...Qf6. Note that it's unlikely a bishop pair can be retained in this position, as White can start the exchange by 14.Nd5 Bxd5.