Mix ingredients for creamy dill sauce in a bowl. Cover and set aside.
Heat a cast iron skillet over high heat until very hot (this can take a couple of minutes- see notes for other skillet types). Turn on your oven fan- it can get smoky!
Pat the shrimp as dry as you can. Cover with the blackening seasoning (3 tablespoons), pressing it into the surface of each shrimp on all sides.
Add butter to the hot skillet until melted. Cook shrimp in butter (2 tablespoons) on medium-high heat on both sides until cooked (2-3 minutes on each side).
Meanwhile, toast corn tortillas in a dry skillet or over your gas burners, or just microwave them to soften a bit (no need to toast flour tortillas, but I do recommend warming them up).
Serve tacos by distributing equal amounts of shrimp in the 8 tortillas spread with the creamy dill sauce, topped with shredded cabbage/lettuce.
The dill sauce is a variation on this easy dill dip - you can make a bunch, use some for these tacos, and use the rest for something else!
You can also make the dill dip ahead of time to make prepping the tacos even faster.
To make your own blackening seasoning, you can mix together: 1 teaspoon paprika, 1/2 teaspoon kosher salt, 1/2 teaspoon black pepper, 1 teaspoon dried oregano, 1 teaspoon dried thyme, 1/2 tablespoon garlic powder, and 1/4 teaspoon cayenne pepper.
Don't have a cast iron skillet? Use another heavy skillet. Other types, like stainless steal or nonstick, won't take as long to heat up as cast iron.
To thaw frozen shrimp: place the shrimp in a bowl of ice water, mixing up occasionally so they don't stick together, for about 20 minutes until they're defrosted. Alternatively, you can run cool water over the frozen shrimp in a colander until they're thawed. You can also place the shrimp on a plate covered in plastic wrap, or in a container, in the fridge for about 24 hours before you're planning on cooking. Drain any liquid that collects at the bottom of the plate before patting dry
If you don't want to use the dill sauce, you can use plain sour cream or Greek yogurt, and/or any other taco toppings such as salsa, hot sauce, avocado, etc.