How to get Trueflame - Elder Scrolls: Morrowind
Trueflame is a weapon that you craft during The Blade of Nerevar Story Quest in the Tribunal Expansion Pack. The Blade of Nerevar is the penultimate quest of the Tribunal Expansion Pack and requires a bit of running around to complete. If you'd like to see a walkthrough for this quest follow the link provided.
During this quest you'll receive an unechanted version of the blade from Yagak the smith which you'll need to take to Radac Stungnthumz in Bamz-Amschend. It's the dungeon that you gain access to midway through the Tribunal Expansion Pack's storyline. You'll find Radac Stungnthumz in the Radac's Forge section of Bamz-Amschend.
After bringing Radac Stungnthumz a bottle of Pyroil Tar he'll take your unenchanted Trueflame and slap a nice little fire enchantment on it for you. You'll need to return to Amalexia to complete the quest (if you want), however at this point the weapon is technically ours and no further action is required.