What is wrong with my tomato?
Once a tomato has a tiny fungal infection or nick, either the fungus will expand or bacterial rot will get in and the fruit rots like the ones you see. The fungus could be anthracnose or alternaria, it doesn't matter. In each case, the solution is to pick the fruit as soon as it colors and bring it inside to ripen. It will not cause the flavor to be bad and it protects your fruits from rot. Tomatoes do not need sunlight in order to produce good flavor once it begins coloring. With all the rain and humidity we have had, fungi are having a heyday. Bring your tomatoes in.