Authentic Supplication Number 203.

The Messenger of Allah  said: When one of you eats let him invoke the name of Allah the Exalted at the start, but if he forgets to mention the name of Allah the Exalted at the start, then let him say: Bismillah, 'awwalahu wa'akhirahu (222).

Footnotes.
(222) In the name of Allah, start of it and end of it.

Reporters.
Reported by At-Tirmithi and he said it was comely-sound and Al-Albani agreed. Al-Albani said it had another channel and a testimonial. He said: See Shar ibn Illan (183-182/5) Al-Albani included this hadeeth in The Authentic of Good Sayings as #144.