The 17-year-old came off the bench during the 4-2 FA Cup replay win.
Onomah, only 17, came off the bench as Spurs secured progression to the next round of the FA Cup.
The north London side, however, did things the hard way, as ever - coming back from 2-0 down in what was already a replay against Sean Dyche's Burnley side.
Tottenham did end up 4-2 winners, though, and Onomah was given the special feeling of making his Spurs debut. Here was his reaction:
Onomah has four assists in 13 games for Tottenham's under-21 side this term and has also featured on the bench twice in the Europa League this season.
Onomah was wearing the number 47 shirt as he came on and this will no doubt be a memory that will stay with him forever.
The 17-year-old will hope there are plenty more memories to come and Spurs' next clash is against Sunderland in the Premier League on Saturday afternoon (3pm kick-off).