I would just take his food away for a couple of hours before you give it and then put it in tuna, tuna is great becuase its really strong smelling.
I had to give my cat antibiotic tablets twice a day for about a week, and either he never worked out what was going on, or he just decided he liked his tuna too much.

Some cats can be crafty as Steph has said, so just keep a close eye on him for a few mins following giving him the tablet.

As for the ham ravioli idea, sounds great, but would it be easier to poke it inside a small chunk of chicken or other meat where you can just make a little hole to poke it inside.

Also, I think I have see in pets at home some cat treats that are designed for hiding tablets in.

Good Luck!