[Mondial]

Yes, if you have a true RMS meter and are measuring in AC mode then you will get an accurate measurement. Calculating E squared over R with the RMS AC voltage will give the true power dissipated in the resistor

If you are using a DC voltmeter (or the RMS capable meter in DC mode),  it will only measure the average DC value of the complex pulsed waveform, not the RMS value and the power calculation will be inaccurate.