1. Bring broth and clam juice to a simmer in a medium saucepan (do not boil). Keep warm over low heat.
2. Melt butter in a large saucepan over medium heat. Add shallots to pan; cook 2 minutes or until tender, stirring frequently. Add rice and saffron to pan; cook 30 seconds, stirring constantly. Add lemon juice to pan; cook 15 seconds, stirring constantly. Stir in 1/2 cup hot broth mixture; cook 2 minutes or until the liquid is nearly absorbed, stirring constantly. Add remaining broth mixture, 1/2 cup at a time, stirring constantly until each portion of broth is absorbed before adding the next (about 18 minutes total).
3. Stir in tomatoes; cook for 1 minute. Stir in shrimp and scallops; cook for 4 minutes or until shrimp and scallops are done, stirring occasionally. Remove from heat; stir in cream. Sprinkle with parsley, if desired.