Answer: Not really. Martian regolith may be heated with microwaves. Considering this “easy” is a stretch. The two most common components of regolith are certainly not “easily” heated with microwaves.
According to https://labs.seprosystems.com/what-happens-when-you-microwave-rocks ,
“Some rocks, like those made of silica, are microwave transparent. And so the microwaves will pass through … For other materials that are highly magnetic, the materials are too conductive and microwaves will be reflected. However, materials with semi-conducting properties, such as sulfides and different metal oxides, heat very well in response to microwaves. Because ores are typically composed of different phases with different microwave properties, some phases heat while others do not.” Blockquote
Martian regolith is mostly composed of silica (it’s concentration is divided by 10 in the graph below) and oxides of metals (iron [also divided by 10], aluminum, magnesium, calcium, and sodium),sulfur trioxide as well as reduced metals (nickel, zinc).
https://en.wikipedia.org/wiki/Martian_soil
So, the major component of regolith is silica, which is transparent to microwaves. Bad news for a Martian microwave smelter. According to https://space.nss.org/settlement/nasa/spaceresvol3/appendixa.htm, impurities may improve absorption above that of pure silica material.
The next must common component is ferrous oxide. According to https://web.p.ebscohost.com/abstract?direct=true&profile=ehost&scope=site&authtype=crawler&jrnl=10735623&AN=61265244&h=c5LLkiVb5SNo61U16vCnYDBo2AgaeZe6ZvAlLM2cmRk3jQmOgeXNA9rKWpUfjgm0JXRRgjdmjB04Jd6E4nZlEw%3d%3d&crl=c&resultNs=AdminWebAuth&resultLocal=ErrCrlNotAuth&crlhashurl=login.aspx%3fdirect%3dtrue%26profile%3dehost%26scope%3dsite%26authtype%3dcrawler%26jrnl%3d10735623%26AN%3d61265244 ferrous oxide absorbs microwaves poorly until heated to 550-1100*C
Bottom line: the minerals which make up the bulk of Martian regolith are poor absorbers of microwaves. A work-around would be to heat the regolith “conventionally” with direct solar thermal energy before turning on the microwave oven. This would bring the ferrous oxide up to a temperature at which it could absorb the microwaves. But if you need to build a solar thermal smelter, why not let it do the whole job? Solar panels, energy storage and microwave generators seem overly complex if direct solar thermal can do the job.