For the pickled onions
- 1/2 red onion
- 1/4 cup white vinegar
- 1/2 tsp kosher salt
- 1/4 cup water
- 2 tbsp sugar
For the adobo sauce
- 1 ancho chili, stemmed and seeded
- 1 tablespoon vegetable oil
- 1/2 small yellow onion, finely sliced
- 1 medium clove garlic, grated on a microplane
- 1 teaspoon dried oregano
- 1/2 tablespoon cider vinegar
- 1/2 tablespoon adobo sauce from can of chipotles
- 1/2 cup crema or greek yogurt
- 2 teaspoons fresh lime juice
- Kosher salt and freshly ground black pepper
- 1 pound asparagus, bottoms trimmed, cut into 1-inch segments
- 6 corn tortillas
- Queso fresco or queso cotija
- Fresh cilantro leaves
- Lime wedges
Place red onion in a medium mixing bowl. Heat vinegar, water, sugar, and salt in a small skillet over high heat, whisking until sugar is dissolved. Bring to a boil, then pour over onions. Press onions down with a spoon until submerged. Stir occasionally and allow to sit until onions are softened and liquid has cooled, about 25 minutes.
Meanwhile, heat ancho chili in a medium saucepan over high heat, turning occasionally, until toasted and fragrant, about 3 minutes. Transfer to a microwave-safe measuring cup and cover with 1/2 cup water. Microwave on high heat until just simmering, about 3 minutes. Let steep until chili is softened. Drain, reserving liquid.
Heat 1 tablespoon oil in now-empty skillet over medium-high heat until shimmering. Add yellow onion, and cook, stirring frequently until softened and lightly browned, about 8 minutes. Add garlic and oregano and cook, stirring frequently, until fragrant, about 30 seconds. Add vinegar, chipotle sauce, and reserved chili liquid. Scrape up browned bits from bottom of pan. Transfer contents to jar of a blender along with soaked chili, crema, and lime juice. Blend on high speed until completely smooth, about 1 minute. Season to taste with salt and pepper and set aside.
Heat remaining tablespoon oil in a large skillet over high heat until smoking. Add asparagus, season with salt and pepper, and cook without moving until well charred on bottom, about 2 minutes. Toss and repeat, allowing asparagus to char before tossing again. Repeat until all asparagus is charred and softened, 8 to 10 minutes total. Transfer to a large plate.
Spread a tablespoon of sauce over tortilla, then top with asparagus, onions, cheese, and cilantro. Serve immediately with lime wedges and extra sauce.
Serves 2. From Serious Eats