Impedance matching for amplifier output
Yes, you can use an L-C network to match your load. It will be very frequency-specific, but as long as you're operating at a fixed freqeuncy, that shouldn't matter too much. But it does mean that it will need to be "tuned" for your application.

A 2:1 transformer would be a more broadband solution, but you definitely cannot use a power transformer designed for 50/60 Hz power, which has a laminated iron core that would be far too lossy at 500 kHz. A large toriodal ferrite core would be much more appropriate.

It might be more appropriate to ask this on Amateur Radio.SE &mdash; some hams work at these frequency and power ranges.