Is ther a standard circuit/component to control the temperature 500W resistive heating element from a PCB?
The easiest way, and probably the one that will yield the best control, is to buy an industrial temperature controller with some kind of serial interface, and switch either a power relay or an SSR with the output. That buys you the thermocouple front end, properly isolated from ground so a fast sensor can be used, an auto-tune PID algorithm and a user display. 

Power relays are inexpensive and reliable, however they wear out after about 100,000 operations at full current. At 20 seconds per cycle, that's a couple  years operating 24/7. If you derate the contact capacity you can get considerably longer life. 

SSRs generate heat (albeit not much at only a few amperes, but will generally require a heatsink) and tend to fail more randomly, and generally fail 'on', which is often an issue. 

In either case, if the controller being stuck 'on' or 'off' could possibly cause significant injury or damage you'll need a redundant backup such as a thermal fuse or an independent limit controller.