Preheat your oven to 425 degrees.
On a large baking sheet, spread the cubes of bread in a single layer, sprinkle with olive oil, salt, and pepper. Toss to combine.
Toast the bread in the oven for 10 minutes until slightly golden brown, flipping halfway through. It should have a bit of a crunch.
In a large, pretty bowl add the toasted bread cubes, onion, cucumber, and tomatoes (with all of their juices). Toss it together with kitchen tongs or salad spoons.
Add the dressing; toss to combine.
Add the torn basil leaves, if using.
Serve immediately.