Pat steaks dry using paper towels, and sprinkle all sides with salt and pepper. Heat 2 tablespoons oil in a large cast-iron skillet over medium-high until just smoking. Add steaks, and cook, turning every 3 minutes, until browned on all sides and a thermometer inserted into thickest portion of steaks registers 130°F to 135°F for medium-rare, 6 to 8 minutes, or to desired degree of doneness. Transfer steaks to a cutting board, and let rest for 5 to 10 minutes.
Meanwhile, place roasted peppers, pistachios, sun-dried tomatoes, miso, sherry vinegar, soy sauce, paprika, garlic, and remaining 2 tablespoons oil in a blender; process until miso romesco is mostly smooth, about 25 seconds.
Slice steaks against the grain. Spread about ¼ cup miso romesco on each plate, and arrange steak over top. Sprinkle with flaky salt, and serve.
