In a small mixing bowl, whisk together the sea salt, cumin, chili powder and paprika.
Pat the steaks dry with a paper towel and arrange on a plate or clean work surface. Lightly season both sides of each steak with half of the spice mixture, pressing it so it sticks to the meat.
In a large cast iron skillet, heat 1 tablespoon of olive oil. When the pan is smoking hot, add the steaks and cook until deeply browned on both sides and semi-firm to the touch, about 3-4 minutes per side for medium-rare. Remove to a cutting board to rest for at least 10 minutes before cutting.
Pour the remaining olive oil into the pan. Add the potatoes and cook over medium-high heat, stirring occasionally, until brown and tender, about 15 minutes. Turn the flame down if they begin to blacken. Add the shallot, kale and remaining spice mixture. Sauté 3 minutes more, until the shallot is soft. Drizzle with the lime juice and remove from the heat.
Thinly slice the steak against the grain into 1/4-inch thick slices. Arrange the steak on top of the potato mixture, garnish with cilantro, and serve directly in the skillet for a rustic presentation!