With Brahmāyu 7.1

7.1

Atha kho bhagavā tathārūpaṃ iddhābhisaṅkhāraṃ abhisaṅkhāsi yathā addasa uttaro māṇavo bhagavato kosohitaṃ vatthaguyhaṃ.

So the Buddha used his psychic power to will that Uttara would see his private parts sheathed in a foreskin.