Wash and dry produce.

Halve, peel, and thinly slice half the onion; dice remaining onion. Drain and rinse beans. Quarter lime. Finely chop cilantro. 

In a medium bowl, stir together sliced onion, vinegar, 1 tsp sugar (2 tsp for 4 servings), a pinch of salt, and pepper. Cover with plastic wrap and microwave 30-60 seconds.

Refrigerate until ready to serve, stirring occasionally.

Heat a drizzle of oil in a large pan over medium-high heat. Add diced onion and cook, stirring occasionally, until softened and fragrant, 3-4 minutes.

Add chorizo, beans, and Mexican Spice Blend; season with salt and pepper. Cook, breaking up meat into pieces, until chorizo is browned and cooked through and beans are warmed through, 4-5 minutes. (TIP: If there’s excess grease in your pan, carefully pour it out.)

Remove from heat; stir in a big squeeze of lime juice.

Place tortillas on a clean work surface. Sprinkle one half of each tortilla evenly with half the cheddar and half the Mexican cheese blend. Using a slotted spoon, top cheese with filling, then sprinkle evenly with remaining cheddar and Mexican cheese blend. Fold tortillas in half to create quesadillas.

Wipe out pan used for filling; heat a large drizzle of oil in same pan over medium heat. Add quesadillas and cook until tortillas are golden brown and cheese melts, 3-4 minutes per side. (For 4 servings, work in batches if necessary.) Transfer to a paper-towel-lined cutting board.

Cut quesadillas into wedges.

Divide quesadillas between plates and top with a dollop of sour cream, pickled red onion (draining first), and cilantro. Serve with remaining lime wedges on the side.