Combine the tomatoes, oregano, cumin, salt, and pepper in the slow cooker. Mix everything together.
2 cans diced tomatoes with garlic and onions, 2 teaspoons dried oregano, 1 teaspoon ground cumin, 1½ teaspoon Kosher salt, ¼ teaspoon "Hot Shot" pepper
Add the bell peppers and onion, then stir again.
2 red bell peppers, 1 sweet onion
Nestle the pieces of beef in the vegetables.
1½ lbs London broil or flank steak
Cook, covered, until the meat is tender, about 7-8 hours on low or 4-5 hours on high.
Without taking the beef out of the pot, shred using two forks.
Stir to mix the shredded beef with the liquid and vegetables.
Garnish with sliced avocado and chopped cilantro to serve.
1 avocado, 1 handful fresh cilantro