I fried my Fluke DMM while measuring voltage across a BBQ Piezo spark igniter. How to fix?
The multimeter has a maximum voltage rating of approximately 1000 volts (1 kilovolt).
Piezoelectric spark generators can provide voltage pulses of over 16 kilovolts.
So you killed your multimeter by exceeding the rated voltage limit by about tenfold.
It is not repairable any more.