Peel pears, leaving stems intact. Cut off one side of each pear so it will lay flat.
Combine water and lemon juice in a large saucepan, bring to a boil; Add pears, return to boiling; reduce heat and simmer, covered, for 10 to 15 minutes or pears are tender. Drain; place pears in a dish cover. Chill 3 hours, or overnight.
Thaw raspberries if frozen Combine raspberries, orange juice, splenda, and cornstarch in a small saucepan. Cook and stir until thick and bubbly, cook and stir 2 minutes more.
Press through a fine sieve, discard seeds . Cover and chill until serving time.