Soo I suppose the joke is the bread burns all too easily despite multiple attempts to get it better? XD
Fun short, though a couple points make it a bit hard to follow I think:
1. Since it's in black and white, it's not obvious the bread's actually burnt more than it's supposed to. Maybe if it was entirely black/maybe also smoking it'd give a more burnt impression.
2. Since you don't see the burnt bread getting thrown away with each new piece (or any other sign of frustration with the character) you wonder the first couple times if maybe it's just an endless loop of a toaster; no pun.
Nicely animated otherwise! Keep it up.
-cd-