See timeit()
Note though that timeit() deals with elapsed time rather than cpu time -- but it takes a number of steps to try to reduce inaccuracies in calculation.
If that is not specific enough for your purposes, then use .NET assembly to access the CPU cycle counters.https://www.mathworks.com/matlabcentral/answers/44352-cpu-cycles-count-for-simulink-model#answer_54380
Note: many "large enough" MATLAB operations automatically use multiple cores, and getting the CPU cycle counts will not total the CPU cycles across multiple cores. CPU cycle counts are not nearly as meaningful as one might hope.