
Add the chiles to a small pot and cover them with water until they're completely submerged. Bring the water to a boil over high heat, then remove it from the heat, cover, and let the chiles soak for 10 minutes.
Using a slotted spoon, transfer the softened chiles to a large blender. Add the tomatoes, onion, garlic, and salt. Puree until completely smooth. Taste and season with more salt, if necessary. If the sauce is too spicy, add more tomatoes.
Heat the oil in a large sauté pan or skillet over medium-high heat. Add the shrimp and cook for 1 minute per side, or until shrimp is light pink.
Pour in the blended red chile sauce and mix together to coat the shrimp. Reduce the heat to medium and cook for 3 to 5 minutes, until the sauce is bubbling and hot.
Remove the pan or skillet from the heat and serve alone as an appetizer or with Mexican Rice as a meal.