I have never had this problem before, but on one of my brandy wine plants, many of the tomatoes have problems like this around the stem:

This tomato actually fell off before it reached peak ripeness due to this decay.

I have looked at a ton of diseased tomato pictures, but don't see anything like this as it is not soft rot or mold really. There is black stuff... almost like little black balls and a hollowed out area. Could it be a weird pest? The damage is always around the stem.

Anyone know what this is and/or how to treat it? There are around 40 more large green tomatoes on this plant that I hope to get to ripen fully.

Thanks in advance,

Robin

I am in the SF Bay area btw, so nothing that could be caused by rain is doing this.