The remaining part of the tomato will be deep red in color. Nothing can be done about this disorder other than making every effort to minimize the removal of excess foliage. Tomatoes that are exposed to the sun during the developing and ripening period do not suffer usually from this problem. Sun scald usually shows on tomatoes that were initially party covered by foliage and then were exposed by the removal of the foliage during pruning or for some other reason. We call it catfacing when the surface of the tomato is deeply ridged and indented.
Tomato specialists attribute the deformity to poor pollination.
When night temperatures go below 55-60 pollination is poor. Likewise excessive heat can reduce pollination. Often-times blossoms will drop without setting fruit. Those that remain are not fully fertilized, and as a consequence they develop improperly. Some varieties of tomatoes are subject to catfacing more that others.