Preheat your oven to 425°F and line a baking sheet with parchment paper.
Slice the Russet potato into thin wedges, toss with olive oil and sea salt, and spread in a single layer on the baking sheet.
Roast the potatoes for 25 to 30 minutes, flipping halfway through, until they are golden brown and crispy.
While the fries roast, season the flank steak evenly with cumin, garlic powder, and chili powder.
Heat a cast-iron skillet over medium-high heat and sear the steak for 3 to 4 minutes per side for medium-rare.
Remove the steak from the pan and let it rest for 5 minutes before slicing it into thin strips against the grain.
In a small bowl, mash the avocado with lime juice until smooth.
Assemble the dish by placing the roasted fries on a plate, layering with the sliced steak, dollops of Greek yogurt, mashed avocado, diced red onion, and fresh cilantro.