How to beat knights as Tau

Title basically.

A friend of mine is new to 40k, but has bought around 3000 points worth of Tau. They were told by other friends to run heavy broadsides to counter knights, but that hasn't seemed to work for them.

We have a knight-heavy local group. Assuming that money is not an issue and they can get any models suggest here, what are the best models and strategems to beat knights with?

(I am not super familiar with Tau. I run chaos cults and my solution to everything to pray to the dark gods and then throw a bucket of dice at any problem.)