Preheat oven to 325°F (180°C) and adjust rack to center position. In a large bowl, toss bread cubes with a drizzle of olive enough to coat them. Transfer to a rimmed baking sheet. Bake about 15 minutes, until crisp and a golden color. Remove from oven and let cool.
Place chopped tomatoes in a colander set over a bowl and season with 2 teaspoons kosher salt. Toss to coat. Set aside at room temperature to drain, tossing occasionally, while you bake the bread and prep the other ingredients. Drain for a minimum of 15 minutes.
Remove colander with tomatoes from bowl and leave in the sink.
To the drained tomato juice in the bowl, add the onion, garlic and 5-6 tsp vinegar. Drizzle and whisk in a 1/4 cup of olive oil. Season dressing to taste with salt and pepper and adjust amount of oil and vinegar to your liking.
Prep the washed and dried basil by bunching up the leaves and with a knive, make 3-4 cuts rough cuts across the leaves. You want to end up with large pieces of basil.
Combine toasted bread, tomatoes, and dressing in a large bowl. Add basil leaves. Toss everything to coat and season with salt and pepper. Let rest 10-15 minutes before serving, tossing occasionally until the dressing is absorbed by the bread.