Crispy corn tostadas topped with a bed of avocado-dressed romaine lettuce, flavorful seared flank steak, tangy pickled red onions, and crumbled blue cheese, served with fresh lime wedges.
1. Preheat oven to 400F convection (or 425F regular bake).
2. Make the pickled onions: Place 1/2 a medium red onion, sliced in thin strips, in a heat-safe bowl or jar. In a small pot, add 1/2 cup white vinegar, 1/2 cup water, 1 tbsp sugar, and 1 tsp kosher salt. Bring to a simmer, stirring until the sugar and salt dissolve. Pour the hot liquid over the onions and let sit at room temperature while you prep the other ingredients.
3. Prep steak: Season the 8 oz flank steak generously with kosher salt and pepper on both sides and set aside at room temperature.
4. Make the tostada shells: Coat a large baking sheet with 2 tbsp avocado oil. Place 6 corn tortillas on the baking sheet and rub both sides in the oil. Sprinkle with some salt and bake for 6 minutes on the first side, flip, and bake for 3-5 more minutes until golden brown and crispy.
5. Make the dressing: Add 1/2 a medium ripe avocado (peeled & pit removed), 1 small garlic clove, 2 tbsp fresh cilantro leaves, juice from 1 lime, 2 tbsp olive oil, 1/4 cup water, 1/4 tsp kosher salt, and 1/8 tsp pepper to a blender. Blend until smooth. Add a bit more water if needed to thin the dressing out.
6. Cook the steak: Preheat a cast iron skillet over medium-high heat for 4-5 minutes until smoking, then add 1 tsp oil. Sear the steak 3-6 minutes per side (timing will vary depending on the thickness) until the internal temperature reaches 130-135F for medium rare. Remove from the skillet and let rest for 5 minutes, then slice into small cubes.
7. Assemble tostadas: Toss the 2 hearts of romaine lettuce (sliced in thin strips) in the avocado dressing. Place a small bed of lettuce on each tostada shell. Top with blue cheese crumbles, sliced steak, and pickled onions. Serve with lime wedges and enjoy!
