Preheat oven to 400°F.

Toss bread cubes in a large bowl with olive oil and a pinch of salt. Spread on a baking sheet and toast for about 10 minutes, until golden and lightly crisp but still a bit chewy.

Set a colander over the mixing bowl and place tomatoes in the colander. Sprinkle with salt and gently toss. Let sit for a few minutes to drain their juices into the bowl.

Remove the colander. In the tomato juice, whisk in vinegar, olive oil, garlic, mustard, thyme (if using), salt, and pepper to make the dressing.

Add tomatoes, toasted bread, shallots, basil, and mozzarella (if using) to the bowl. Toss everything gently until well combined.

Let the salad sit for 20 to 30 minutes at room temperature so the bread can absorb the dressing without getting mushy.

Toss once more before serving. Garnish with extra basil if desired.