What does he mean, he doesn't want it? How dreadfully wasteful. Ungrateful man! Bung some sauce over it - he'll never know the difference.
<Waiting to see how long it is until someone takes me seriously>
I like the lemon idea. If that doesn't work this might (but involves ammonia - probably not a good idea if you have small children or animals around and don't know if it is readily available)
You need a glass bowl, and half a cup of household ammonia.
Preheat the oven to 200 degrees Fahrenheit and turn it off. Pour half a cup of household ammonia into a glass bowl, and place it on the centre shelf of the oven. Make sure that you do not inhale the vapors. Close the door and leave the ammonia inside the oven overnight. The next day, allow the ammonia vapors to escape. Keep people from entering the kitchen. As soon as the vapors are gone, clean up the oven with a damp dish towel.