In a small saucepan, bring broth and quinoa to a boil. Lower the heat, cover and simmer until broth is absorbed and grains are tender, 20 to 25 minutes.

Slice the top off each tomato. Use a spoon to hollow out pulp and seeds and reserve the pulp and seeds in a bowl. Chop the tomato tops and add to the bowl. Set bowl and tomato shells aside.

Preheat oven to 400°. In a large skillet over medium heat, combine the onion and 2 tablespoons water. Cook, stirring frequently, until onion begins to brown, about 6 minutes. Stir in garlic, scallops, raisins, thyme, salt, pepper and reserved tomato trimmings and cook, stirring frequently, until most of the liquid has evaporated, about 5 minutes. Stir in cooked quinoa, basil and vinegar.

Stuff the tomato shells with quinoa mixture and arrange the stuffed tomatoes in an 8 x 8-inch baking dish. Bake for 15 minutes, or until the tomatoes are soft and filling is just browned on top.