Bright-green Castelvetrano olives add a sharp, sweet, and briny finish to this classic hummus. Slideshow: More Hummus Recipes
Chop 1/2 cup of the olives coarsely, and chop the remaining 1/4 cup finely. Using a mortar and pestle, pound the garlic, anchovy, and the capers to a paste. Add the chopped olives, parsley, and olive oil and pound lightly a few more times to combine. Season with a squeeze of lemon juice, to taste. Set aside.
In the bowl of a food processor, combine the chickpeas, tahini, garlic, olive oil, lemon juice, cumin, cayenne pepper, salt and pepper, and process until smooth. Adjust the consistency of the hummus with 3 tablespoons of water and scrape down the sides of the bowl. Pulse a few more times until incorporated and smooth. Taste to adjust for seasoning and transfer to a serving dish. Spoon the tapenade over the hummus and serve alongside warm pita bread.
The hummus can be refrigerated for up to 1 week. Bring to room temperature to serve.