Place pesto ingredients in a food processor and pulse until well combined, but still a little coarse in texture. Place in a bowl and store in the fridge until the chicken is ready. Preheat the grill to medium-high. Combine the oil, lime zest, cumin, salt and pepper in a bowl. Add the chicken and turn to coat. Grill 3-4 minutes per side, or until cooked through. Serve chicken with a generous spoon of the pesto alongside.