What is causing this to happen to my tomatoes?

Wow! I have never seen anything like this. I will be curious as to a remedy myself. Are all the tomatoes like this? I would email this photo to your local Ag Extension and see what they have to say.

bloom rot. this comes from too much watering and can be improved with Epsom salt . use 1 TSP in a gallon of water and water from the bottom sparingly.

Unfortunately I’ve seen this befor...insect damage Is one possibility a fungus is the other. Some times bloom end rot can look like this...

I think that's Blossom End Rot. I get some like that every year. Try reading this: https://commons.m.wikimedia.org/wiki/File:Blossom_end_rot.JPG#mw-jump-to-license. I hope this helps.

When you plant your tomatoes you should put about 2 tablespoons of Epsom salt in the hole and mix it up with the dirt--then plant. And if you water your tomatoes with the Epson salt and water mixture about every 3 weeks you should not have this problem. And yes--water from the bottom--not over the plants. Tomato plants do not like to be really wet so if you get a lot of rain--cut way back on watering them--if at all.

honestly it is not blossom end rot it is a disease causing deformed tomatoes.Have you rotated you plants from last year, did you have issues any any time in the past?

keep all leaves off the ground.

Well Sam it's still called blossom end rot and it's caused by calcium deficiency, you can buy a product at Lowes to mix in a spray bottle and just spray the plants every day, at the end of the growing season put down lots of lime

keep all leaves off of the ground

War15939090 has it right. Your tomatoes need calcium. I'm a Master Gardener. You have blossom end rot. All of the plants in the same family (tomatoes, potatoes, eggplant, etc) will get it from calcium deficiency. go to the web site of the extension office of your state university and look for it...

It's blossom end rot. It can occur because of uneven watering practices or a calcium deficiency in the soil. Epsom salts do help because they add magnesium to the soil, which helps the plant take up more calcium.

Sorry to be remiss in resolving this problem! Concensus was blossom end rot, which turned out to be absolutely right! Added calcium to the soil and it seems to have corrected the problem! So thanks again to everyone who assisted me!