Preheat an oven to 350°F (175°C).

To make the tiny torn bread crumbs, cut the loaf in half and use your hands to tear the inside bread into tiny pieces, about the size of peas. Save the outside to dry out and use for traditional bread crumbs another time. Place the torn bread pieces on a baking sheet and bake until lightly toasted, 8 to 10 minutes. Set aside to cool before using. This yields about 3 lightly packed cups (3 3/4 oz./115 g) crumbs; you will use all of them for this recipe. Leave the oven on.

Cut the stem off of each tomato top and remove the core (or just some of it—you don’t want a hole in the bottom of the tomatoes when you fill them) as needed. Using your fingers or the end of a teaspoon, gently remove most of the seeds from the tomato halves without changing their shape.

Place the tomatoes, cut side up, on a baking sheet and sprinkle liberally with salt. Bake until you can see the tomatoes beginning to release liquid and soften slightly, about 10 minutes.

Remove from the oven and turn the tomatoes upside down on a wire rack set over a baking sheet to release their extra juices while you make the persillade mixture. Leave the oven on.

Smash and use one of the garlic cloves to rub the inside of a large gratin dish (or similar baking dish). Drizzle the dish with olive oil, using your hands to coat the bottom and sides. Using a sharp knife or mezzaluna, finely chop the parsley and remaining garlic. In a medium bowl, combine the parsley-garlic mixture, and bread crumbs. Season the persillade mixture with and drizzle with about 1/4 (2 oz./60 ml) and toss to coat all the bread crumbs evenly.