Using kitchen scissors, cut along both sides of the backbone of each bird; remove and discard the spine. Cut the birds in half along the breast bone, and then press down firmly with a rolling pin to flatten.
Place the butter in a small bowl, then beat in l tbsp (15ml) of the olive oil, the garlic, thyme, cayenne, salt and black pepper, half the lemon and lime rind, and l tbsp (15ml) each of the lemon and lime juice.
Carefully loosen the skin of each poussin breast with your fingertips. Using a round-bladed knife or small palette knife, spread the butter mixture evenly between the skin and the breast meat.
Preheat the grill and line a grill pan with foil. In a small bowl, mix together the remaining olive oil, lemon and lime juices, and the honey. Place the bird halves, skin side up, on the grill pan and brush with the citrus juice mixture.
Grill on one side for 10-12 minutes, basting once or twice with the juices. Turn over and grill for 7-10 minutes, basting once, or until the meat juices run clear when the thigh is pierced with a knife. Garnish with the dill. Serve with grilled tomatoes and a salad.