Police are investigating the circumstances that led to the man named locally as Darren Paul Turner attacking the woman at her home in Granadilla de Abona, in the south of the island, last Thursday.
After burning her face with a blowtorch, the alleged perpetrator then used a rock to hit her. He was arrested along with a 47-year-old German man who was with him at the time of the attack.
After the assault, the pair left the injured woman on the floor of her home to go out drinking in a nearby plaza.
The woman, who is reported in 20 Minutos newspaper to be 36-years-old, suffered third degree burns to her face and is being treated in intensive care at the Hospital Nuestra Señora de La Candelaria.
On his arrest, the Brit man reportedly told police: "I killed my friend", according to the local La Opinion newspaper. He had injuries consistent with a suicide attempt and is being treated at a secure medical unit.
"We can confirm the arrest of a British National on April 1st in Tenerife," a spokesman from the British Embassy in Madrid told The Local. "We are providing consular assistance."