"List question" is an ambiguous term. You can't just slap the name on anything with more than one answer and call it not constructive/not a real question/off-topic.
Some list questions are clearly bad - in general, anything with dozens of equally valid answers is going to start getting out of control, like a "good cookbooks" question. It's open-ended, broad, solicits discussion, polling... all of these are explicitly cited reasons to close questions. This is why in general, list questions are a bad idea - they tend to be questions that meet the criteria for closing. It's not the other way around; they're not closed because they're list questions. Polls are in this category, as are many shopping questions.
Some list questions are fine: they don't have a whole lot of different answers, so they don't really meet the explicit criteria for closing questions. This is why we allow some kinds of culinary use questions. While they may have many good individual answers, they're not infinite; you could reasonably expect one posted answer to cover most of them. For example, there are a lot of ways to make homemade ice cream soft.
I claim that my question falls into the latter category. There are only so many basic traditional cooking methods that translate easily into the microwave. Yes, there are many things you can find a way to do - that's why there's an "ask a question" link at the top of the page, and why there's already for example a question about how to scramble eggs in the microwave. But the scope of this question question is limited to not include those things, making it quite answerable, and the question does not solicit polling or discussion (except for this meta-discussion).
Appendix: Something like this has been asked many times on various site metas as well as meta-SO (going back to before *.stackexchange.com existed). A few examples:
(genealogy) "How can we word the FAQs to make clear the site policy on list questions?"
(SO, from linguistics) Is there a canonical source I can link to / quote from to back up “list questions are bad”?
(SO) Should we have a “List of X” close reason?
(SO) Are list questions off topic?
(UX) List questions - another take
(SO, back when community wiki was more common) Should polls be maintained as Community Wiki questions, or should they be closed?
If you read through all of this, I think it's fair to say that there's a lot of debate about how exactly to draw a line between good and horrible list questions, and about how to explain this concisely (e.g. in the FAQ), but that the rough consensus is that there is such a line, and it's not all the way at one end or the other. There are also a lot of problems caused by the fact that people tend to lump all list questions in one bucket, expecting them all to be either all okay or all bad.