That's actually exactly what existing MCF machines do. The gyrotron (ECRH, same as a microwave's magnetron) resonant frequency is tuned to the confinement fiel

That's actually exactly what existing MCF machines do. The gyrotron (ECRH, same as a microwave's magnetron) resonant frequency is tuned to the confinement field strength of the plasma so it absorbs the energy. On top of that there's a vacuum so air doesn't pull all the heat away and a magnetic bottle so the plasma doesn't touch the wall. Fusion is very far away from happening spontaneously on Earth.