One question, what if the plates both touch the steak and I use a
smaller voltage? I guess since steak is conductive, keeping the plates
at a 1V/cm potential may actually sink a lot of current through the
steak and cook it after all.

Sure, you can have the plates touch the meat. If it's 1cm thick, put a
volt across it, and you're done.

As you point out, though, if you put that field on the meat itself
(whether by direct contact, or because it's suspended between two plates
with air in the middle), current will flow, and heat will be dissipated.
Your exercise is to figure out how much, and how hot it gets.

Assume the thermal capacity is the same as water.
I'd assume the conductivity is about the same as sea water (60 mS/cm) as
a start.