The key to authentic Key Wat is a long and slow cooking process. The sauce (wot) is built on a base of long-braised onions (sometimes without fat initially) and then enriched with Niter Kibbeh (spiced clarified butter).
If you don't have Niter Kibbeh, you can use Ghee and add cardamom, turmeric, and a pinch of ginger to it. Adjust the amount of Berbere spice to your tolerance for spicy foods.
In a large pot or Dutch oven, start braising the onion dry over medium-low heat. Braise for about 10–15 minutes until most of the water has evaporated. Add Niter Kibbeh (or Ghee) and continue sautéing for 5 minutes until the onion is caramelized and soft.
Add garlic and ginger and sauté for another 2 minutes.
Stir in Berbere spice and tomato paste. Sauté for 3 minutes until the spices absorb the fat and release their aroma.
Add the cut beef. Sear the meat on all sides to seal in the juices. Lightly salt the meat.
Pour in the water or broth. The liquid should almost cover the meat. Bring to a boil, then reduce the heat to minimum (it should only gently bubble), cover, and simmer for 2 to 3 hours.
The goal is for the meat to be extremely tender, falling apart, and the sauce thick and rich.
Stir halfway through cooking and check the consistency. If it's too thick, add a little hot water. If it's too thin, cook uncovered for the last hour.
Serve the Key Wat hot, layered on a large Injera flatbread, surrounded by mild vegan Wot, such as Kik Wat and other side dishes, which form the Beyaynetu.