Landing page using external domain / duplicate content

I am a bit of a newbie as far as this issue is concerned. So, kindly bear with me with the following question:

Example:
I am running wordpress on domain https://www.main-website.com.

Now I would like to create a landing page within that wordpress installation >> i.e. https://www.main-website.com/landing-page.

BUT I want to use another domain to point to that page >> https://www.great-product.com directs to https://www.main-website.com/landing-page.

To prevent duplicate content I would like https://www.main-website.com/landing-page to be indexed via https://www.great-product.com instead of https://www.main-website.com/landing-page.

Other pages of https://www.main-website.com should however be indexed normal.

Any idea how to do this or a nice alternative?

Thanks,
Flowrian