4 oil-packed anchovy fillets, soaked in cold water for 15 minutes and patted
1/4 cup snipped chives
1/2 cup chopped arugula
1 cup extra-virgin olive oil
1/4 cup salt-packed capers, soaked in cold water for 1 hour and drained
1/4 cup chopped sage
Preheat the oven to 450°. Using kitchen scissors, cut out the backbone. Flatten the chicken and pull out the breast bone. Cut the chicken in half through the breast and season with salt and pepper. Set the chicken skin side up in a roasting pan and drizzle with the oil; add the lemon halves to the pan and roast for 40 minutes, basting every 10 minutes, until just cooked through.
Meanwhile, make the salsa verde. In a food processor, pulse the capers with the anchovies and garlic until finely chopped. Add all of the remaining ingredients and pulse to combine. Season with salt. Serve the chicken with the salsa verde and the roasted lemon.