It looks like your tomatoes may have sunscald, which happens when developing fruit is exposed to excessive sunlight. There are fungal/bacterial diseases such as anthracnose and tomato spotted wilt virus than can show similar characteristics. Anthracnose doesn't usually affect green tomatoes. Symptoms of tomato spotted wilt virus can affect leaves and stems. The leaves and stems on your tomato plant look healthy so I think sunscald may be the problem with your tomatoes.

Here is some information on sunscald and other problems of tomatoes.  

Tomato Fruit Problems.pdf (missouribotanicalgarden.org)

Troubleshooting Cultural Problems in Tomatoes | UGA Cooperative Extension

Tomato Diseases & Disorders | Home & Garden Information Center (clemson.edu)

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