I promised to cook a treat/'thank you' meal either tonight or tomorrow for the couple I've been staying with, but have no idea what my lack of experience would permit me to make. I am really scared of whipping something up and it being totally tasteless or just plain gross.

What can all you serious cooks out there recommend as a simple but delicious meal to serve for dinner?
(Preferably nothing with bacon, and if possibly I would like to avoid dairy, but that is not a big factor)