Wash and dry all produce. Adjust rack so that it is about 8-inches from flame and preheat broiler to high. Halve, peel, and thinly slice onion. Quarter tomatoes. Cut lime into wedges. Thinly slice scallions. Trim root end from lettuce, then slice leaves into thin shreds.

In a small bowl, stir together sour cream, Southwest seasoning, and a squeeze or two of lime. Season with salt and pepper. Set aside.

Heat a drizzle of oil in a large, ovenproof pan over medium-high heat. Add onion and cook, tossing occasionally, until softened, 4-5 minutes. Season with salt and pepper. Add taco spice and 1/4 cup tomato paste (we sent more) to pan. Stir until fragrant and wellcombined, about 1 minute.

Add beef to pan, breaking up meat into pieces. Cook, tossing occasionally, until browned, 4-5 minutes. Season with plenty of salt and pepper. Stir in 2 TBSP water, then sprinkle cheese over top. Transfer pan to broiler and broil until cheese is melted and bubbling, about 3 minutes. Sprinkle with scallions.

While everything’s broiling, wrap tortillas in a moistened paper towel. Microwave on high until warm and soft, about 30 seconds.

Arrange lettuce, tomatoes, lime wedges, and crema into bowls or plates for serving. Fill tortillas with beef mixture and divide between plates. Let everyone add the toppings as they like and dig in!