Place steak on a quarter sheet pan. Mince 4–6 cloves of garlic to get 1 tablespoon minced garlic. Spread 1 ½ teaspoons garlic onto top side of steak; season with 1 teaspoon dried oregano, 1 teaspoon salt and ½ teaspoon pepper.
Flip steak and rub remaining 1 ½ teaspoons garlic, 1 teaspoon oregano, 1 teaspoon salt, ½ teaspoon pepper on second side. Cover with plastic wrap and refrigerate for at least 4 hours or up to overnight.
When ready to cook, cut 1 pepper and 1 onion into large chunks. Smash 5 cloves of garlic.
Remove steak from refrigerator and cut in half cross wise, then cut halves into 1 ½-inch-thick strips along the grain.
Add pepper and onion chunks, smashed garlic, wine and 3 cups water to a large sauté pan over high heat. Nestle steak into vegetable mixture; bring to a boil then reduce to a simmer over medium heat and cook, partially covered, until beef is tender and can be pulled apart with forks, about 1 ½ hours. (Or 40 minutes in a pressure cooker on high.)
Using tongs, transfer steak to a bowl or sheet pan; allow to cool.
Pour vegetable mixture through a fine mesh sieve into a liquid measuring cup; reserve solids and liquid. Wipe out sauté pan.
Thinly slice remaining onion and peppers and chop 3 garlic cloves.
Heat 3 tablespoons avocado oil in a sauté pan over medium-high heat, add sliced peppers and sliced onion; season with salt and cook, stirring frequently, until starting to soften, about 5 minutes.
Using your hands, or two forks, shred cooled meat.
Add shredded beef and chopped garlic and fry, over medium-high heat, until browned and charred but still tender, 15–20 minutes, stirring every 3 minutes or so. After first 10 minutes, you may need to occasionally deglaze pan with reserved simmering liquid.
Meanwhile, bring 1¼ cups water to a boil in a saucepan. Add rice, bring to a simmer, cover and cook over low until rice is tender and water has been absorbed, 10–12 minutes. Remove from heat, fluff with a fork, cover and let steam until ready to serve.
Chop reserved simmered pepper and onion mixture and add to a bowl with black beans; stir to combine and season with salt and pepper to taste.