Spicy Beef Stew from Eritrea

Directions

In a large pot over medium heat, add 30ml of olive oil.
Once the oil comes to temperature, add in two finely diced red onions. Be sure to dice them as finely as possible so they break down fully, leading to a smooth stew.
Sauté the onions slowly, stirring constantly until the very beginnings of caramelization are evident. Just a little bit of color.
Next, add in 75g of berbere powder, and stir thoroughly, making sure each piece of onion is coated. It should absorb all the moisture in the pot, and turn into a paste.
Now add 125ml of water, and stir until a thick sauce forms.
Sauté until the mixture is looking jammy, then add in a 28oz (800ml) can of tomato puree. Be sure to rinse out the can with a little water, and dump that water into the pot as well.
Season thorougly with salt and freshly cracked black pepper, bring to a simmer, then cover and cook for 30min, stirring regularly.
After 30min, add 1kg of diced beef, as well as two sliced serrano chilies.
Cover and continue to cook for 30min.
Add 100g of butter, and when melted, serve atop injera bread.