Well I've herd drying you're bud in the microwave can lead to vaporized THC within 10sec or less. Just because it's being suspended in butter dosen't change the outcome. I would just let it warm at room temp, if I were you.
FYI...Don't microwave cannabudder to defrost it.Let it defrost on it's own.I found that microwaving definitely affects the potency. I made a batch (1 lb.) ,used 1/2 & froze 1/2. My cookies with the first batch were awesome.(great buzz) .On my second batch , I microwaved the budder for 30 seconds to thaw it. Now you have to eat 2 cookies to get a small buzz.I thought it was just me, so I had a buddy try one and he didn't even get high.
Now I know better.