How to Make It
Preheat the oven to 400°. Cut the top third off each tomato and reserve. Scoop out the seeds and flesh from the tomatoes, leaving thin but sturdy walls. Sprinkle the tomato shells with 1/2 teaspoon of salt and turn them upside down on a rack to drain for 30 minutes.
Meanwhile, warm the milk in a small saucepan. Remove from the heat and add the bread. In a medium skillet, heat 2 tablespoons of the olive oil. Add the onion and cook over moderate heat until softened, about 5 minutes. Add the garlic and cook until fragrant, about 1 minute. Add the sausage and cook, breaking up the pieces with a wooden spoon, until browned and no longer pink inside, about 8 minutes. Add the lettuce and cook until wilted, about 1 minute. Remove from the heat and let cool.
Remove the bread from the milk and squeeze dry. Add the bread, parsley, basil and eggs to the sausage mixture and stir to combine. Season with 1 teaspoon of salt and the pepper.
Set the drained tomato shells in a gratin dish and fill with the stuffing, mounding it slightly. Set the tomato lids on top. Drizzle the remaining 1 tablespoon of olive oil over the tomatoes and bake for about 20 minutes, or until the tomatoes begin to collapse and wrinkle. Serve hot or at room temperature.