That ‘stripe’ was probably Blossom End Rot. It’s caused by a lack of calcium.
Give your tomato plants some powdered or liquid bone meal to prevent this in the rest of the ripening fruit.
It’s not a disease; it’s a nutrition issue. Calcium is the first element that leaches out of our soil, and most of us don’t have a lot of calcium in our soil in the first place.
For future reference, throw a handful of powdered bone meal into the planting holes of tomatoes, peppers and cucumbers and zucchini. They can all get Blossom End Rot.
It won’t hurt you, but you should try to prevent it in the rest of your ripening fruit. Do a dressing on your cukes, zukes and peppers if you’re growing those, too. :)
OK that explains why some folks say put crushed egg shells on top of the dirt in a layer.