Four fire engines and around 25 firefighters were called to a fire at a shop with flats above on Burnt Oak Broadway in Edgware.
Most of the shop on the ground floor was destroyed by fire.
The Brigade was called at 1313 and the incident was under control by 1432. Fire crews from Stanmore, Hendon and Willesden fire stations were at the scene.
The cause of the fire is believed to be an electrical fault in a microwave.