Tuna baked in foil

I had a single 6 oz yellowfin tuna steak and didn't want to dirty a pan.  So I seasoned it well, wrapped it in foil and baked it in the toaster oven for 20 minutes.  It turned out fine, but was a little overcooked.  The foil made it hard to judge doneness as you can when you pan sear it. 

I got two servings out of it.  The leftover 2.5 ounces will make a nice tuna salad sandwich. 

Do you bake in foil?  How do you time it? 

I've cooked tilapia filets like that a couple times. Just add a small amount of butter, a little garlic powder, and some lemon pepper.

I had it in at 350 for about half an hour. I don't know how I figured that... after a while I opened up the pouch and the fish looked done. Tilapia is pretty hard to mess up, though!