Make sure to dry the shrimp on paper towels very well. Transfer them to a bowl.
Drizzle the shrimp with a lug of olive oil and season well with the seas salt, Mexican seasonings, smoked paprika, garlic and onion powder. Use a wide spatula and Toss to coat well all over.
Allow the seasoned shrimp to rest at room temperature for 15 minutes.
Meanwhile work on the heirloom salsa fresca. Dice the tomatoes and toss together with the scallions, chile pepper, cilantro leaves and lime juice. Season to taste with the sea salt and set aside.
Preheat a cast iron pan over medium high heat for a a few minutes.
Using a pair of tongs add the shrimp to the hot skillet. Sear for about 45 seconds on each side until it curls up and is golden brown on both sides. Transfer the cooked shrimp to a plate and keep warm while charring the tortillas.
Place each tortilla on a burner with low flame until nice charred marks form. About 30 seconds or so, keep a close eye on them so they don't burn.
Assemble your tacos by placing the shrimp inside the charred tortillas, spoon some of the salsa Fresca on top and a light drizzle of crema or sour cream. Garnish with cilantro and the chile pepper slices to taste.
Serve with the lime wedge to squeeze on top right before the first bite !