Adjust an oven rack to the middle position and heat the oven to 400°F. Spread the bread pieces on a rimmed baking sheet and toss with two tablespoons of the olive oil and a pinch of salt.

Bake the bread until the edges are golden and crisp, about 10 to 15 minutes, stirring halfway through the baking time.

Place the tomatoes in a colander set over a large bowl and season with salt. Let them drain for 15 minutes — this concentrates the tomato flavor and provides the base for the vinaigrette.

Whisk the remaining olive oil, red wine vinegar, and pepper into the collected tomato juices in the bowl. Add the toasted bread pieces and toss until they are evenly coated.

Let the bread sit in the dressing for about 10 minutes to absorb the flavors. It should feel moistened but still retain a bit of crunch at the center.

Add the tomatoes, cucumber, shallot, and basil to the bowl. Fold gently to combine and serve immediately, while the bread still has a slight chew against the juicy tomatoes.