Update an item with the most recent linked item from another board

Board A has a list of Authors. (Screenshot: Imgur: The magic of the Internet )

Board B has a list of Posts, which includes a Date field as well as a field that’s connected to the Authors board. Some Authors appear in multiple Posts records. (Screenshot: Imgur: The magic of the Internet )

I would like to add a “Most Recent Post Date” to the Author board that, well, shows the date of the most recent Post in the Post board that’s attributed to a given Author.

So, I need two things:

1. A way to update the entire Authors board with the current “Most Recent Post Date” values.
2. An automation to update the Authors board any time a new Post is added to the Post board.

Any suggestions? Thanks!