What causes tomatoes’ skins to split at the stem?
Planted Legacy or Beefsteak tomatoes in April using a Lifetime(TM) plastic raised garden bed, 4'L x 4'W x 18" D. Used organic garden soil from Lowe's. Tomatoes have thrived until heavy rains through month of May. Now, several tomatoes have been partially eaten by snails while several more have multiple splits (5-6) in the skin starting from the stem and extending on the upper quarter of the fruit's crown.
Fluctuations in temperature can be the cause, as well as heavy rains or dry spells.
Mulching can be a help.