CB tops may show little, if any, return...but turbulence can be severe.
At high altitude cruise it is a good idea to select maximum gain (if available on your specific radar installation) and this gives you an increase of 3881 percent power (Collins WXR 700X Pilots' Guide) above the AUTO gain. This increase in radar power will often show up CB tops as a small echo whereas nothing will show up on AUTO. Once you pick up this tiny echo, you can adjust gain and tilt to suit closer interpretation.