2 cups loosely packed fresh parsley
3 scallions, coarsely chopped
2 tablespoons capers, drained
Zest and juice of 1/2 lemon
2 anchovy fillets
2 cloves garlic, smashed
1/2 teaspoon dijon mustard
1/3 cup extra-virgin olive oil, plus more for the grill
1 flank steak (about 1 1/2 pounds)
Freshly ground pepper
2 or 3 medium tomatoes
Make the salsa verde: Pulse the parsley, scallions, capers, lemon zest and juice, anchovies, garlic, mustard and olive oil in a food processor until slightly chunky. Pour into a bowl and season with salt.
Preheat a grill to high or place a grill pan over high heat. Pierce the steak all over with a fork and season with salt and pepper. Oil the grill or pan; grill the steak, 4 to 5 minutes per side for medium-rare, turning once. Transfer to a cutting board and let rest for 5 minutes.
Slice the tomatoes and season with salt and pepper. Thinly slice the steak against the grain. Serve with the tomatoes and salsa verde.