The magneto-optical Kerr effect (MOKE) is commonly used in time-resolved measurements of magnetization. A technique is presented to amplify this rotation and improve the signal-to-noise ratio in measurements of the very small polarization changes that are needed to measure magnetization reversal in single domain nanomagnets. The largest cavity-induced enhancement to date, a factor of 16.25, was observed. Enhancement of up to three orders of magnitude is possible with optimized structures.