1. Heat 1 tablespoon oil in a large Dutch oven over medium-high heat; swirl to coat. Add onion; sauté 1 minute. Add garlic; reduce heat to medium. Cover and cook 8 minutes, stirring occasionally. Add wine and next 5 ingredients (through tomatoes); cover. Bring to a boil; reduce heat and simmer, uncovered, 15 minutes.
2. Sprinkle snapper and scallops with black pepper. Heat a large skillet over high heat. Add remaining 1 tablespoon oil; swirl to coat. Add snapper and scallops; cook 90 seconds on each side or until golden brown. Add snapper, scallops, shrimp, and clams to broth mixture. Cover and cook 4 minutes or until clams open; discard any unopened shells. Stir in parsley and lemon juice.