Pat the shrimp dry. Moisture is the enemy of browning. Use paper towels to dry both sides. This helps the spices stick and the shrimp sear instead of steam.
Mix the spices. In a small bowl, combine chili powder, smoked paprika, cumin, garlic powder, onion powder, cayenne (if using), salt, and a few grinds of black pepper.
Season the shrimp. In a large bowl, toss shrimp with 1 tbsp olive oil, half the lime zest, and the spice mix until evenly coated.
Set aside for 5–10 minutes while you prep the sauce.
Make the avocado sauce. In a blender or food processor, combine avocado, Greek yogurt, garlic, lime juice, cilantro (if using), salt, and 2 tbsp water. Blend until smooth. Add more water, 1 tsp at a time, until it’s a pourable but thick sauce.
Taste and adjust salt or lime.
Prep your toppings. Shred cabbage, slice radishes, and chop cilantro. Set out lime wedges and any salsa or hot sauce you like.
Warm the tortillas. Heat a dry skillet over medium-high. Warm each tortilla 20–30 seconds per side until soft and lightly charred in spots.
Keep them wrapped in a clean towel to stay warm and pliable.
Cook the shrimp. Heat 0.5–1 tbsp olive oil in a large skillet over medium-high. Add shrimp in a single layer. Cook 1.5–2 minutes, flip, and cook another 1–2 minutes until opaque and just firm.
Squeeze over the remaining lime zest and a bit of lime juice. Do not overcook.
Assemble the tacos. Layer cabbage on warm tortillas, add shrimp, and spoon over the avocado sauce. Finish with radishes, cilantro, and a squeeze of lime.
Add hot sauce if you like heat.