In the bowl of a food processor or blender, combine 1 cup parsley, 1 tablespoon freshly minced garlic, 1/8 cup fresh oregano, 2 1/2 tablespoons red wine vinegar, 1/4 teaspoon red pepper flakes, 1/4 teaspoon kosher salt, 1/4 teaspoon freshly cracked black pepper. Blend. While blending, slowly pour in 1/2 cup extra virgin olive oil until the mixture is combined. Pour into a serving container, cover, and refrigerate until ready to use.
Heat a cast-iron skillet on mid-high heat and season each steak with 1/4 teaspoon kosher salt, 1/4 teaspoon sugar, & 1/8 teaspoon freshly cracked black pepper on both sides. NOTE: The sugar helps to achieve a nice crust on the steak and enhances the flavor of the beef.
Place the steak(s) in the hot, dry skillet and allow to sear for 3 minutes, without moving. You want to get a nice caramelized crust on the outside of the steak.
When the steak has a nice sear on the one side, use tongs and turn the steak over. Add 1 tablespoon of garlic butter to the pan and sear the steak for 2-3 more minutes (or until your desired temperature) while basting with the butter. Don't move the steak, just spoon butter over the top while it sears. Remove from heat and allow to rest for 10 minutes before slicing.
Cooking time will vary depending on how you like your steak. For best results, use an instant read thermometer to check for desired doneness. I cook my steaks between 125° and 130°F. If you like them more done, be sure to adjust the cooking time accordingly.