Buffy & Spike in Revello Dr Kitchen. Drop of Spikes blood on counter. Buffy tastes it.

Spike went out the back door. Buffy sees a drop of his blood on the counter. She swipes it with her finger and tastes it. Meanwhile, Spike is walking across the yard when he feels a jolt.

I believe it is Old Friend, Long Gone by Darkrivertempest. The first chapter has a scene like you described. It's a very good fic. It's on this site and Elysian Fields.

This is it! Thank you so much!