Ok so you don't mean accuracy you mean resolution. Even so :-
At 50KHz, that is 50000 HZ and the resolution you need is 0.01 HZ, so you need to control one part in 5,000,000, but you can double that because you have to set the output high and low for a cycle of output.
So for a processor running at 16MHz you need to be changing the output every 1.6 clock cycles. So can you see you can't do this?