With a stainless steel knife, peel and core the pears. Cut them into eighths. Rub them with lemon so they do not discolor. Set them aside in a covered bowl in the refrigerator until you are ready to use them. Melt the butter in a large skillet. Saute the pears over high heat for 3 to 4 minutes or until they begin to brown. With a slotted spoon, transfer the pears to a serving platter. Deglaze the pan with liqueur and raspberry preserves and reduce until syrupy and thick. Spoon over the pears and garnish with almonds and frozen yogurt or whipped cream if you wish.