For an extra smoky flavor, use a charcoal grill or add wood chips to your gas grill. If you don't have a grill, you can also cook the steak in a hot cast-iron skillet. Feel free to add other toppings to your tacos, such as pickled onions, cilantro, or a drizzle of hot sauce. For a spicier crema, add a pinch of cayenne pepper or a few drops of your favorite hot sauce to the blender.