Heat up 1 tablespoon of cooking fat in a large skillet placed over medium heat.
2 tbsp. cooking fat
Toss in the onions and garlic and cook for about 4 to 5 minutes.
1 large sweet onion, 1 garlic clove
Transfer the onion and garlic to a plate and set aside.
In the same skillet, add the other tablespoon of cooking fat and keep it at medium-high heat.
2 tbsp. cooking fat
Add the beef to the skillet. Cook for about 6 minutes, or until browned to desired doneness, and set aside.
1 lb. flank steak
Add the bell peppers and shallots, and cook until the peppers start to soften (about 5 minutes).
3 shallots, 3 bell peppers, Sea salt and freshly ground black pepper
Toss the onions and beef back into the pan. Cook until everything is warm (about 2 minutes), and serve.