Preheat the oven to 400 degrees F. In a small mixing bowl, stir together the cereal, 2 teaspoons of the parsley and half of the chopped garlic.
Cut the tops off the tomatoes and reserve. Carefully scoop out the tomato pulp, leaving the tomatoes intact, and place in a medium mixing bowl. Stir in the shrimp, rice, vermouth, if using, lemon zest, olive oil, remaining chopped garlic, remaining 2 tablespoons parsley, 1/2 teaspoon salt and 1/4 teaspoon pepper.
Place the tomato cups in a baking dish and fill evenly with the rice mixture. Top generously with the crumb mixture and drizzle with olive oil; top with the tomato tops. Bake until the rice is cooked through, about 1 hour. Serve warm or chilled.