Before starting, wash and dry all produce. Add onions, vinegar, 2 tbsp water and 2 tsp sugar (dbl both for 4 ppl) to a small pot. Season with salt. Bring to a simmer over medium-high heat. Cook, stirring often, until sugar dissolves, 1-2 min. Remove the pot from heat. Transfer onions, including liquid, to a medium bowl. Place in the fridge to cool.

While onions cool, core, then cut pepper into 1/4-inch slices. Roughly chop cilantro. Add sour cream and half the cilantro to a small bowl. Season with salt and pepper, then stir to combine. Set aside.

Heat a large non-stick pan over medium-high heat. When hot, add 1 tbsp oil (dbl for 4 ppl), then peppers. Cook, stirring occasionally, until tender-crisp, 3-4 min. Add beef, Mexican Seasoning, salsa and chipotle sauce. Cook, breaking up beef with a spoon, until fragrant and heated through, 4-5 min.**

Wrap tortillas in paper towels. Microwave until tortillas are warm and flexible, 1 min. (NOTE: You can skip this step if you don't want to warm the tortillas!)

Whisk together 1 tbsp pickling liquid (from the bowl with onions) and 1 tbsp oil (dbl both for 4 ppl) in a large bowl. Add spring mix and remaining cilantro. Season with salt and pepper, then toss to combine.

Drain pickled onions and discard liquid. Divide tortillas between plates. Top with beef filling and pickled onions. Spoon cilantro sour cream over top. Serve salad on the side.