1 lb. thin sirloin steaks (1/2 inch thick each) or 1 lb. flank steak
2 jalapeño or serrano chiles—thinly sliced and seeded (for less heat) or chopped with seeds and membranes (for more heat)
½ small red onion, finely chopped
2 limes, juiced (about 1/4 cup)
4 cloves garlic, grated
2 tomatoes on the vine, seeded and chopped
A handful of fresh cilantro leaves with tender stems, finely chopped
Cayenne hot sauce (I like Frank’s RedHot)
1 large Haas avocado, coarsely chopped
1 tsp. each ground cumin, dried oregano, and chili powder (I like Gebhardt)
3 tbsp. neutral-flavored oil
1 white or yellow onion, chopped
1 bell pepper (any color), seeded and chopped
¼ cup drained mild or hot pickled jalapeño slices
4 large (10-inch) flour tortillas
2 cups shredded Mexican cheese blend, pepper Jack, or Monterey Jack
Mexican crema or sour cream, for serving
Freeze the steaks until slightly firm, about 5 minutes.
Heat a large cast-iron skillet over medium-high to high.
In 2 medium bowls, divide the chiles, red onion, and half the lime juice. Add a quarter of the grated garlic to each bowl; season with salt. Let stand for a few minutes. To one bowl, add the tomatoes, some cilantro, and a few dashes of hot sauce for the pico de gallo. In the other bowl, using a potato masher or fork, mash in the avocado for the guacamole.
Thinly slice the steaks against the grain; season with salt, pepper, and the spices.
Add 2 tbsp. oil, two turns of the pan, to the skillet. Add the beef in a single layer and cook until brown and crispy, 2 to 3 minutes. Turn the beef over and cook until browned, about 2 minutes more. Transfer to a plate.
Add the remaining 1 tbsp. oil, one turn of the pan, to the skillet. Add the white onion, bell pepper, and pickled jalapeños and cook, tossing occasionally, until crisp-tender, 3 to 4 minutes. Add the remaining garlic and lime juice; season with salt and pepper. Mix in the beef and remove from heat.
Heat a nonstick skillet over medium. Spray 1 tortilla lightly with cooking spray and add to the skillet, sprayed-side down. Scatter a quarter of the cheese on top. Arrange about a quarter of the beef and vegetables on 1 side of the tortilla. Fold the tortilla over the filling and cook, turning once, until golden and crispy, 1 to 2 minutes per side. Repeat with the remaining tortillas, cheese, beef, and vegetables.
Cut the quesadillas into wedges. Serve with the crema, guacamole, and pico.