The radiation left over from the Big Bang is the same as that in your microwave oven but very much less powerful. It would heat your pizza only to minus 271.3*C - not much good for defrosting the pizza let alone cooking it.
And in that I cannot send unto you all my businesses in writing I despatch these present bearers fully informed in all things to whom it may please you to give faith and credence in what they shall say unto you by word of mouth.
