Roast the poblano pepper over an open flame or under a broiler until charred, then steam in a covered bowl for 5 minutes, peel, and slice into thin strips.
Peel and dice the russet potato into small half-inch cubes.
Heat the avocado oil in a large skillet over medium-high heat and add the diced potatoes, cooking until they are golden brown and nearly tender.
Add the ground beef to the skillet with the potatoes, breaking it apart with a spatula and browning it thoroughly.
Stir in the diced onion and minced garlic, sautéing until the onion is translucent and fragrant.
Pour in the tomato puree, sea salt, black pepper, and ground cumin, then fold in the prepared poblano strips.
Reduce the heat to low, cover the skillet, and simmer for 10 minutes until the potatoes are soft and the sauce has thickened slightly.