How to Make It
Preheat the oven to 375°. Cut the top third off of each tomato. Using a melon baller, scoop out the tomato flesh, leaving a thick wall all around. Finely chop the tomato flesh and seeds and transfer to a large bowl. Season the tomatoes with salt.
Spread the bread cubes on a baking sheet and toss with 2 tablespoons of the olive oil. Bake until the croutons are browned and crisp, about 8 minutes. Let cool.
In a medium skillet, heat 2 tablespoons of the olive oil. Add the onion and sliced garlic and cook over moderate heat until softened, about 8 minutes. Add to the chopped tomatoes in the bowl.
In a small saucepan, heat the remaining 2 tablespoons of olive oil. Add the minced garlic and simmer over low heat until light brown, about 4 minutes. Let cool completely. Stir in the mayonnaise and lemon juice and season with salt and black pepper.
Add the beans, tuna, celery, parsley, thyme and crushed red pepper to the large bowl and toss. Fold in the garlic mayonnaise and croutons and season with salt and pepper. With a paper towel, pat the insides of the tomato shells dry. Mound the salad into the tomatoes and serve at once.