give me an example of a homophonic pun

Sure! Here's an example of a homophonic pun:

Why did the tomato turn red?

Because it saw the salad dressing! (sounds like "saw the salad dressing" sounds like "sourdressing")

give me a new one

Of course! Here's another example:

Why was the math book sad?

Because it had too many problems, it needed some "solutions"! (sounds like "solutions" - "solu-shuns")