Put the garlic, herbs, capers, lemon zest, herbs, anchovies and chilli flakes into a food processor and blend to a coarse paste. Add the lemon juice, then gradually pour in the oil, while pulsing the blender on a low setting.
When you get a textured paste, taste it and season with salt and pepper to your liking.
Cut the tomatoes in half, put them a bowl and pour over the salsa verde. Set aside.
Heat your grill, BBQ or griddle pan. Rub the steak with some oil and season with salt.
Seal the steak on each side for 30 seconds, then cook it to your liking - turning the meat over every minute or so.
Move the steak to a plate, cover and rest for 5 minutes. Serve with salsa verde and tomatoes.