The AD9833 data sheet says "The DAC generates an output voltage of typically 0.6V p-p".
What percentage does the output voltage varies? (Output voltage variation: 0.6Vp-p +/- xx%) What is xx?
Im sorry but you cannot equalize as there is not direct access to the DAC.
Being said that, you could compensate the effect, an even get a pretty flat transfer function, by using the AD8337 in series.