To prepare broth, peel shrimp, reserving shells. Cover and chill shrimp. Combine shrimp shells, water, and next 7 ingredients (water through quartered onion) in a large Dutch oven; bring to a boil. Reduce heat to medium; cook until reduced to 3 cups (about 40 minutes). Strain broth through a sieve into a bowl, and discard solids.
To prepare pilau, heat oil in pan over medium heat. Add 1 1/2 cups chopped onion, and sauté 5 minutes. Stir in red pepper and tomatoes, and cook 5 minutes. Stir in broth, rice, and 1/2 teaspoon salt; bring to a boil. Cover, reduce heat, and simmer 20 minutes. Fluff rice with a fork. Stir in shrimp; cover and cook 3 minutes or until shrimp are done. Sprinkle with parsley.