Echo top most parent (ancestor) category of a post

My site has the following structure

• Fruit
  • Apples
  • Oranges

I have a post called “Pits”, and Pits is in both the categories Apples, and Oranges.

In my theme, I would like to echo only the top most parent category “Fruits”.
I have tried countless codes but they all seem to only echo the first category parent, and not go one level higher.