Note the present version of the betrayal revelation scene in John:
***
21 When Jesus had thus said, he was troubled in spirit, and
testified, and said, Verily, verily, I say unto you, that one of you
shall betray me.
22 Then the disciples looked one on another, doubting of whom he spake.
23 Now there was leaning on Jesus' bosom one of his disciples, whom
Jesus loved.
24 Simon Peter therefore beckoned to him, that he should ask who it
should be of whom he spake.
25 He then lying on Jesus' breast saith unto him, Lord, who is it?
26 Jesus answered, He it is, to whom I shall give a sop, when I have
dipped it. And when he had dipped the sop, he gave it to Judas
Iscariot, the son of Simon.
***
The scene makes no sense as Simon could not ask the person lying on
Jesus' breast without Jesus overhearing. One can do an experiment and
act out the scene to see how awkward and ridiculous it is.
Other early traditions identify the disciple who Jesus loved as Mary Mag. There is some evidence within the synoptics that this relationship has been edited out reidentifying his loved one as a male and his marriage feast as for another couple. It has been proposed that the last supper scene went more like this:
21 When Jesus had thus said, he was troubled in spirit, and
testified, and said, Verily, verily, I say unto you, that one of you
shall betray me.
22 Then the disciples looked one on another, doubting of whom he spake.
23 Now Jesus was leaning on the bosom one of his disciples, the one
whom Jesus loved.
24 Simon therefore beckoned to her, that she should ask who it
should be of whom he spake.
25 Jesus' lying on her breast she whispered unto him, Lord, who is it?
26 Jesus answered Mary, He it is, to whom I shall give a sop, when I
have dipped it. And when he had dipped the sop, he gave it to Simon
Peter, the son of John.
***
The scene now makes perfect sense. Jesus is lying on Mary's breast,
possibly with eyes closed, so he does not see Simon gesturing to Mary, wispering to her
to ask him about the betrayal.
Some have because of other awkward sections suggested that Peter was the betrayer. Judas Ischariot appears to be a character pulled into the betrayal role from some separate zealot story, perhaps by proto-orthodox editors interested in elevating Peter as their founder. But that is another topic.