spectrum time domain measurement
No.
If you set a spectrum analyzer to "zero span", the display will read the average power level of an RF energy right around where the spectrum anlyzer is tuned. The power meter will act like there is a bandpass filter in front of it, with that filters bandwidth being equal to the "resolution bandwidth".
An oscilloscope, for instance, measures instantaneous voltage (not average power) and shows that trace against time, not power averaged over 1 mS or so.