Slice the flank steak against the grain into thin strips and place in a bowl.
In a small ramekin, combine the chili powder, cumin, smoked paprika, sea salt, and black pepper.
Toss the steak strips with the spice blend and half of the lime juice until evenly coated.
In a separate bowl, toss the shredded cabbage, diced red onion, and remaining lime juice to create a quick slaw.
Heat the olive oil in a cast-iron skillet over medium-high heat. Add the steak and sear for 3-5 minutes until browned and cooked to your preference.
Warm the corn tortillas and black beans in a separate pan or the microwave.
Assemble the tacos by layering the black beans, steak, and cabbage slaw into the tortillas.
Top with sliced avocado and fresh cilantro before serving.