How to get rid of ringing / overshoot
On all real systems a step response also produces an overshoot. 

The designer has to consider the trade off between rise time and overshoot: a faster rise time means more overshoot and but less overshoot normally means a slower rise time.

This is the decision you're making when you're adding the capacitor to low-pass filter the output. Adding this filter reduces your overshoot, but increases your rise time.

You can tune this RC filter to act to your specification. When simulating that can be done experimentally, or you can calculate a cut off frequency:



You want this to be just above the maximum frequency you want your system to output.