But I don't think this one is BER -- The odd appearance is created by fused blossoms -- it looks like at least three, possibly 4th blossom in the center, were fused together -- you may have noticed the sunflower like giant blossom this fruit originated from. Underneath, you can see where the co-joined fruits tried to merge together... and failed... leaving odd gaps her and there and scars where they fused.
These cavities can become hiding places for bugs as well as fungal spores and especially in humid conditions can become a source of spoilage.
Also, typically, the fused blossoms did not mature at the same time so that the earliest blossom to be pollinated will develop a few days ahead of the latest pollinated, resulting in uneven ripening and sometimes spoilage if you wait for the entire lumpy fruit to ripen 100%.... But it looks like you picked this one before they had a chance to blush, so I'm not sure if you will see it ripen.
FWIW -- the candidate fruits for those official Giant Tomato contest that are held world-wide are usually varieties that have been selected for this kind of fused mega blossoms -- those can be as many as 8-10 fruits fused together.
What variety is this?
Learning never ends because we can share what we've learned. And in sharing our collective experiences, we gain deeper understanding of what we learned.