Ingredients

• 1.5 pound beef flank steak, sliced into ¼-inch strips
• 0.25 cup lime juice, fresh
• 3 tablespoon olive oil
• 4 garlic, minced
• 2 teaspoon ground cumin
• 1 teaspoon smoked paprika
• 0.5 teaspoon dried oregano
• 1 teaspoon kosher salt
• 0.5 teaspoon black pepper
• 2 red onions, thinly sliced
• 0.5 cup white vinegar
• 1 tablespoon sugar
• 0.5 teaspoon salt (for pickling)
• 1 ounce refried beans
• 8 corn tostada shells
• 1 cup cotija cheese, crumbled
• 0.5 cup fresh cilantro, chopped
• 2 limes, cut into wedges

Steps

1. Prepare the pickled onions by slicing the red onions into thin rings and placing them in a shallow dish. In a small saucepan, combine white vinegar, ½ cup water, sugar, and ½ teaspoon salt. Heat until just simmering, then pour over the onion rings.
2. While the onions pickle, prepare the beef marinade by combining lime juice, 2 tablespoons olive oil, minced garlic, ground cumin, smoked paprika, dried oregano, kosher salt, and black pepper in a shallow bowl. Mix well.
3. Pat the beef flank steak dry with paper towels. Slice the meat against the grain into ¼-inch-thick strips.
4. Add the beef strips to the marinade, tossing to coat evenly. Let sit for 15 minutes at room temperature.
5. While the beef marinates, warm the refried beans in a small saucepan over medium heat, stirring occasionally. Keep warm but do not boil.
6. Heat a large cast-iron skillet or heavy-bottomed skillet over medium-high heat until very hot, about 2 minutes.
7. Add the remaining 1 tablespoon olive oil to the hot skillet. Working in two batches to avoid crowding, add the marinated beef strips and cook without stirring for 2–3 minutes until a dark brown crust forms on one side.
8. Stir the beef and cook for another 2 minutes until cooked through. Transfer the first batch to a plate and repeat with the remaining beef strips.
9. Return all the cooked beef to the skillet, toss with any pan drippings, and remove from heat.
10. Warm the tostada shells in the skillet over medium heat for 1 minute per side to crisp them and warm through. Transfer to a serving plate.
11. Spread a thin layer of warm refried beans on each tostada shell. Top with a generous handful of the warm carne asada beef.
12. Sprinkle crumbled cotija cheese over each tostada. Top with pickled red onions (drained of excess liquid) and a pinch of fresh chopped cilantro.
13. Serve immediately with lime wedges on the side for squeezing over the tostadas.