To make the sauce, combine the herbs, mayonnaise, sour cream, garlic, lemon juice and salt in a food processor or blender and pulse until smooth. The sauce can be made up to a week ahead.
Season the steaks with salt. Set a heavy (cast iron is ideal) skillet over medium-high heat.
Drizzle some oil into the skillet and when it’s hot, cook the steaks for about 4 minutes, until a deep crust has developed on the bottom.
Flip and cook for another 4-5 minutes (for medium-rare) or until done to your liking.
Let the steaks rest for 5-10 minutes before slicing and serving drizzled with the sauce.