Wash and dry all produce. Zest and quarter lime (for 4 servings, zest 1 lime and quarter both). Halve, peel, and thinly slice onion; finely dice a few slices until you have 2 TBSP (4 TBSP for 4 servings). Finely dice tomato. Halve, core, and slice poblano into 1/4-inch-thick strips.

Rinse shrimp under cold water, then pat dry with paper towels. In a medium bowl, combine shrimp, Southwest Spice, and a squeeze of lime juice. Set aside.

In a second medium bowl, combine diced onion, tomato, a squeeze of lime juice to taste, half the lime zest, and 1/4 tsp sugar (1/2 tsp for 4 servings). Season with salt and pepper.

In a small bowl, combine sour cream with remaining lime zest. Stir in water 1 tsp at a time until mixture reaches a drizzling consistency. Season with salt.

Heat a large drizzle of oil in a large, preferably nonstick, pan over medium-high heat. Add poblano, sliced onion, salt, and pepper. Cook, stirring occasionally, until browned and tender, 6-7 minutes. Transfer to a plate. Add a large drizzle of oil and shrimp to pan. Cook until shrimp is opaque and cooked through, 3-4 minutes. Stir in juice from remaining lime wedges. Season with salt and pepper.

Meanwhile, wrap tortillas in damp paper towels and microwave until warm, about 30 seconds. Divide between plates and fill with shrimp and veggie filling. Top with pico de gallo and crema. Serve.