Blossom end rot

From Freepedia

Blossom end rot is a nutrient deficiency affecting several garden plants, including eggplant, tomato, and peppers. The disease starts as sunken, dry decaying areas start at the blossom end of the fruit, furthest away from the stem.

While the outward appearance of the fruit is that it is affected by a disease-causing pathogen, the disorder is actually the result of calcium deficiency. This may be the result of low soil calcium levels, incorrect fertilizer selection, ion competiion, or drought stress. Sometimes rapid growth from high-nitrogen fertilizers may cause blossom end rot.

Example of blossom end rot on Roma tomatoes