Heat a large skillet over medium-high heat. Add the duck fat and allow to melt.
Place both steaks in the skillet and cook for 3-5 minutes.
Flip the steak and cook five minutes more, or until you have reached your desired doneness. Use a meat thermometer to check.
Remove steak from the heat and allow to rest 10 minutes.
Heat your tortillas while the steak is resting. You can char them directly over the flame of a gas stove burner, heat them up in the oven, or microwave them.
Cut steak into thin strips.
Have fun building your tacos! Add your strips of steak, warm roasted potatoes, black beans, and your favorite toppings.