Slow Cooker Carne Mechada Tacos

Ingredients

• 1-1 1/2 pounds flank steak
• Kosher salt
• Freshly ground black pepper
• 1 teaspoon onion powder
• 1/2 teaspoon ground cumin
• 1 teaspoon olive oil
• 1/2 cup diced tomatoes in purée
• 2 cloves garlic, minced
• 1 yellow onion, cut into wedges
• 1 small bunch cilantro, leaves and stems
• 1 bay leaf
• 2 teaspoons brown sugar
• 1 teaspoon Worcestershire sauce
• 1/2 teaspoon red chili flakes
• 1/2 cup pale lager
• 1 small yellow onion, diced
• 1 clove garlic, minced
• 1/2 cup chopped cilantro leaves, plus more for garnish
• Warm tortillas
• Shredded cabbage
• Avocado
• Jalapeño
• Quick-pickled red onions
• Sour cream
• Cilantro and lime wedges, for serving