Browning the outer external surface of a foodstuff with infrared rays emitted from an infrared source at the same time the interior of the foodstuff is processed in an electronic range. The foodstuff and the source for emitting the infrared rays are placed in a region where electromagnetic waves are radiated from a high frequency generator. The infrared source is constructed by evaporating a conductive thin film on the outer surface of a dish or other vessel for holding the foodstuff. Alternately, crystallized glass having fine pieces of carbon fibres scattered throughout may form the infrared source. In yet another embodiment, a layer of silicon carbide may be formed on an insulating base plate. In each of the embodiments, the infrared heat is generated by the action of the electromagnetic waves on the specially constructed source.