To make the pistachio butter, add the pistachios to a food processor and pulse until small powdery crumbs remain. It’s okay if there are a few larger pieces. Add the butter to a bowl and stir in the pistachios, mixing well to combine. I like the butter to be a bit chilled, so either place the bowl in the fridge or scoop the butter into a piece of plastic wrap and mold it into the shape you’d like before sticking it in the fridge. (Note: this makes a pretty good amount of butter so if you want less, cut the recipe in half. Or just save it and put it on EVERYTHING.)
To make the salsa/slaw, combine all of the ingredients in a large bowl and toss well to combine. Place the slaw in the fridge until ready to use.
To make the crispy tortillas, heat a large skillet (I like to use a cast iron skillet and then I’ll cook the fish in the same one) over medium-high heat. Add the olive oil about 1 tablespoon at a time and once it’s hot, add a tortilla to the skillet and cook on each side for about 1 minute. The tortillas should be golden and slightly puffy. Remove each from the skillet and allow them to rest on a paper towel to cool, then tear them into pieces.
Pat the fish completely dry with a paper towel – this is important because it helps the outside of the fish to crisp up. Season both sides of each piece with the salt, pepper, paprika and garlic powder. (If you love any other spices, you can add them in here.) Heat a large cast iron skillet over medium-high heat. You want it hot. Once hot, add the olive oil and butter. As soon as the butter melts, add the sea bass into the skillet and cover, cooking for about 3 minutes. Gently flip the fish (it should be deeply golden and crisp on the skillet side – if it isn’t, your skillet needs to be hotter) and cover the skillet again, cooking for an additional 2 to 3 minutes. Turn off the heat and keep the skillet covered for another 1-2 minutes. Remove the cover and scoop a small amount of pistachio butter on top of each filet. Serve immediately with the slaw and crispy tortillas.