Why does this plum/apricot hybrid look like brains?

Notes:

• Here's a photo of what a normal fruit on the tree looks like.
• Location is Zone 5, east of Toronto.
• There are about 20 other fruits on the tree. This the only fruit on the tree that has this problem.
• The date is June 26, 2019 (although plants have been delayed by about 3 weeks this year due to unusually cool and rainy weather).
• I have had lots of disease problems on my prunus this year due to the wet weather.