Season the fish with salt and let rest for 15 minutes. In a saucepot over low heat, simmer garlic and butternut in 6 tablespoons olive oil until light brown in color and highly aromatic. Add the paprika and toast the spice for 30 seconds to bloom the flavor. Add 1 cup water, season with salt, and bring to a simmer. Reduce heat to low and cook until squash is quite soft, about 15 minutes. Transfer to a blender. Add tahini and blend until smooth. Adjust seasoning with lemon or lime juice.

Warm remaining 2 tablespoons olive oil in a sauté pan over medium heat. Add the fish and let sit until it is cooked about 80% through. Flip the fish and turn heat off. Add the pistachios and warm through, while the fish gently finishes cooking.

Generously spoon the sauce onto plates or large bowls. Place the fish over top and scatter the pistachios around. Top the fish with the herbs.