Prepare a grill for high heat and thoroughly clean grates. Arrange the shrimp on metal skewers (or wooden skewers that have been soaked in water for at least 1 hour). Brush the shrimp with the oil and season with ½ teaspoon salt on both sides.
Grill shrimp, turning once, until just starting to turn opaque and slightly charred, about 1 minute per side. Transfer to a platter and set aside to cool. When cool enough to handle, remove from skewers.
Heat a large cast iron skillet over medium heat and melt the butter. Cook the onion, chile poblano, celery, chile serrano, garlic, oregano, coriander and ½ teaspoon salt, tossing occasionally. Cook until the onion and chile poblano are beginning to brown, for 6 to 8 minutes. Add the tomato and cook, tossing frequently and scraping up any browned bits, until the tomato begins to break down, for about 5 minutes more. Transfer to a large bowl.
Add the grilled shrimp to the bowl and toss to combine. Taste and season with salt.
Wipe the skillet clean with a paper towel. Working in batches, place the tortillas in the skillet and top with about ¼ cup of shrimp filling each. Add a small mound of cheese on top of the filling and fold over like a taco. Cook until the cheese is beginning to melt and the tortilla is lightly toasted, for 2 to 3 minutes. Flip to toast the second half. Continue with the remaining tortillas, cheese, and shrimp.
Serve with a squeeze of lime and your favorite salsa.
