Answer: 1. Bc2. This blocks the pawn from moving and so creates a sort of ultimate zugzwang. The first and only player at the Utah Closed to find this together with all the variations was Vinh Tran. (I finally found it too but wasn’t playing in the tourney and so had more time to study the position, but we still split the pot anyway. Hopefully you noticed that, 1.b8(Q)+ doesn’t work because d6+ and White must honor the check rather than move Qc5.)