Pat the steaks dry. Season all over with kosher salt and black pepper.
Heat olive oil in a large skillet over medium-high heat. Sear steaks until well browned, about 2.0 to 3.0 minutes per side. Transfer to a plate.
Reduce heat to medium. Add sliced onion and cook, stirring, until softened, about 5.0 minutes. Add minced garlic and cook 0.5 minute until fragrant.
Pour in white wine and simmer, scraping up browned bits, until reduced by about half, 2.0 to 3.0 minutes.
Stir in crushed tomatoes, dried oregano, and red pepper flakes. Bring to a gentle simmer and cook 8.0 to 10.0 minutes to thicken slightly.
Add capers. Nestle the steaks and any juices into the sauce. Simmer gently until steaks reach desired doneness, about 4.0 to 8.0 minutes depending on thickness.
Turn off heat. Stir in butter (if using), basil, and parsley. Adjust seasoning with additional salt and pepper to taste.
Rest steaks in the sauce 3.0 minutes. Slice against the grain and spoon sauce over to serve.
Notes
For a richer sauce, add a splash of beef broth or a few sliced olives. Serve with crusty bread or over polenta or spaghetti.