It's difficult to provide a certain diagnosis by viewing the photo. However, based upon what we can see, the fruit appears to have been damaged initially by sun scald and secondarily by anthracnose.
The following bulletins discuss sunscald and anthracnose and how the two may be related. We remain a little uncertain because anthracnose is usually most prevalent later in the growing season. Sun scald can occur any time the fruits are overexposed to sun. Heavy pruning or leaf loss due to disease makes the fruits susceptible to sun scald.
Another master gardener suggested that the hole in the fruit might have been caused by an insect. She could be correct. If so, a variegated (AKA climbing) cutworm is a likely suspect.
Tomatoes damaged by cutworms
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