From Everything I have read about this in the past it is caused by long dry spells with infrequent watering. Tomato plants need a lot of water so when it becomes available the plant absorbs as much as it can and this causes the fruit to split. You might want to try mulching your raised beds to help them retain some moisture. Putting down a layer of fall leaves or some wood chips across the top of your bed could help out.

I believe that's called catfacing which results from incomplete pollination. Do a google search. It seems some varieties are more prone to this than others. One website said cool temperatures might be the reason - 60 degrees for a few days three weeks prior to bloom. That sounds like the cool temperatures we had a few weeks ago. Your title "splitting" made me think your problem was the skin cracking when there's too much rain which is something a lot of cherry tomato types do when the tomatoes are ripe but the skin bursts with a fresh crack, not like the dried deformity in your photo. Catfacing may also be the result of too much nitrogen.

I agree with defrost that your plant is catfaced, not split.

All-

Thanks for the advice! I had never heard of catfacing, and couldn't think of how else to describe the issue. However, I think you're right- it's definitely a catfacing issue.

I picked up a soil test kit over the weekend. I'll check the soil, but otherwise keep things going as usual. The plants seem to be growing healthily.

Thanks again for enlightening me!

Bob

I would just put a little more emphasis on the fact that some varieties of tomato are more prone to cat facing than others. I rarely have had that issue and I think it might be the varieties I have used.

I've only had it with certain heirloom tomatoes, not all heirlooms, and never on more "modern" varieties.