In a food processor or blender, pulse the parsley, garlic, anchovies, capers and vinegar until coarsely chopped. With the machine on, slowly pour in 1/2 cup of the oil and mix just until blended.
In a large nonstick skillet, heat the remaining 1 tablespoon of oil until almost smoking. Season the steak and add it to the skillet. Cook the steak over moderately high heat until well seared outside and still pink inside, 5 to 6 minutes per side for medium rare. Transfer to a cutting board and let stand for 5 minutes. Carve the steak across the grain into thin slices. Serve with the salsa verde.
Olive Oil A peppery or pungent extra-virgin olive oil gives the steak's salsa verde an edge.
The beef's piquant sauce calls for a red with sufficient fruity intensity. A hearty Shiraz from Australia is ideal.