My one tomato is black on the bottom. How come?

Question

I have one tomato plant that has good size tomatoes but the under side is black where the top is fine.

Answer 1

This is Blossom End Rot and is from a lack of calcium.
This article will help you.

https://www.gardeningknowhow.com/edible/vegetables/tomato/tomato-blossom-rot.htm