Wash the Yukon gold potatoes and dice them into uniform 1/2-inch cubes to ensure even cooking.
Heat 1 teaspoon of avocado oil in a large cast-iron skillet over medium-high heat. Add the diced potatoes and a pinch of sea salt.
Cook the potatoes for 10-12 minutes, tossing occasionally, until they are golden brown and crispy on the outside and tender on the inside. Remove from the skillet and set aside.
While potatoes cook, season the steak on both sides with sea salt, black pepper, and garlic powder.
In the same skillet, heat the remaining 1 teaspoon of avocado oil over medium-high heat until shimmering.
Place the steak in the skillet along with the smashed garlic cloves and the rosemary sprig. Sear for 3-4 minutes per side for medium-rare, or until your desired level of doneness is reached.
While the steak sears, steam the green beans in a small pot with a splash of water for 4-5 minutes until bright green and tender-crisp.
Remove the steak from the pan and let it rest for at least 5 minutes before slicing against the grain.
Plate the sliced steak with the crispy potatoes and steamed green beans, drizzling any remaining pan juices over the meat.