1D power spectrum from 2D fft

I have a 2D wave function f(x,y) for which I can compute a 2D fft with matlab's fft2 function. Now I would like to plot a wavenumber vs. power spectrum to see what wavenumbers are dominant in f(x,y).

I understand how I can do this in 1D but I don't know how to make sense of 2D power spectra. Is there a way to condense the 2D information into a 1D plot?

Ideas welcome!