can onions be caramalized completely in the microwave? If so, how?
There are tricks with vinegars and other compounds, if what you are after is chemical breaking down of complex sugars into simpler sugars. Sure you can do this in microwave, technically, but it will never produce the flavor you get from contact heat. Microwave will boil and dry the ingredients. Vinegar acts helps to do this in a water solution – here I mean onion juice.

Or you can improvise with surrounding onions with oil – this way you will get microwave-powered deep fryer. This should produce contact-heat-like conditions and caramelization. But then deep fryer would be more energy efficient.

In other words – there is no substitute for contact heat.