My Roma is beautiful- looks like a prize winner Inside has long black rot What is wrong?
Hennepin County Minnesota tomato blossom end rot
Most likely your beautiful Roma tomato has experienced blossom end rot. The same thing happens to my Romas at times, especially the ones I grow in containers. This is not a disease but caused by a calcium deficiency in the tomato. This calcium deficiency is produced by an inconsistent supply of water, which impedes calcium uptake into the plant. Usually this rotting is visible on the outside of the tomato. However, in its early stages it starts inside of the tomato. Here is some information about this condition:
Unless the blackening is extensive, it is possible just to cut it out before eating. At least in my experience, the taste is unaffected by this condition.
Thanks for the question!!