As far as the canon goes, I found four relevant examples, listed in 'in-universe' chronological order:
1) In the Attack of the Clones movie, when Count Dooku has Obi-wan trapped on Geonosis, he tries to lure Obi-wan into helping him overthrow Sidious:
Dooku: What if I told you that the Republic was now under the control of the Dark Lord of the Sith?
Obi-wan: No, that's not possible. The Jedi would be aware of it.
Dooku: The dark side of the Force has clouded their vision, my friend. Hundreds of senators are now under the influence of a Sith
lord called Darth Sidious.
Obi-wan: I don't believe you.
Dooku: The viceroy of the Trade Federation was once in league with this Darth Sidious but he was betrayed ten years ago by the dark lord.
He came to me for help. He told me everything. You must join me,
Obi-Wan, and together we will destroy the Sith!
Though there is some debate as to whether or not he was sincere in this request, see Why did Dooku reveal the truth about Darth Sidious to Obi-Wan on Geonosis?
2) Darth Sidious ordering Count Dooku to kill his assassin/apprentice, Asajj Ventress, in TCW 3x12:
Sidious: Lord Tyranus.
Dooku: My master.
S: There is a disturbance in the force. Your assassin, she has become
D: Yes, my lord. She is quite important to me.
S: Too important. I can sense her powers growing stronger. I would
hate to think you are training your own sith apprentice to destroy me.
D: Never. My allegiance is to you and you alone.
S: Then you must prove it. Eliminate her.
D: She's my most trusted ...
S: I said eliminate her!
D: As you wish, my lord.
3) The part mentioned by ncalmbeblpaicr0011 in TCW 3x13, taken with a grain of salt considering that Sidious had just ordered Dooku to get rid of his previous apprentice, and there wasn't anything further mentioned in TCW about Dooku trying to overthrow Sidious.
4) In the novelisation of Return of the Sith, by Matthew Stover, you can find excerpts referenced in What was Dooku's plan for the Battle of Coruscant? which discuss Dooku's frame of mind towards Sidious at that point.