I worked at Le Cellier, so I am biased... But Le Cellier. The Filet Mignon actually is
AAA Canadian beef from my home province of Alberta
However, if you like a more marbleized cut, the Rib Eye is sooooo good. They usually change up the set that comes with it, so it's probably different than what I had. But the cut on its own is delicious. They also usually top it with a garlic butter, or red wine butter of some sort that is phenomenal. Gives it extra flavour without overpowering the steak.
And if you go to Le Cels, you have to get a Canadian classic.. Poutine! Preferably the Signature or French Onion!