Should be able to spray the pan but you need to flour it too so the batter can climb up.

I've done it both ways and haven't noticed much difference. My DH doesn't like cake and I do so this works just perfectly for me. I, too, usually top it with some kind of fruit and a spritz of whipped cream......Yummy and so easy....:). And I can whip it up any time of the day for whenever....:) I generally just soak the container I make it in with a little Dawn.....washes out with no sweat!

Thanks to all who replied to my post about greasing the mug for the 3-2-1 cake.

This was my thought on the matter, too.