Toss the bread squares in the olive oil and spread them on a baking sheet lined with parchment paper. Parchment is optional if your baking sheet doesn't have an issue with food sticking. Sprinkle the bread with a pinch of salt. Bake until the bread is crispy, or about 15 minutes. Set aside to cool.
For the Salad:
In a large bowl, toss together the grape tomatoes, cucumber slices, and red onion slices.
Sprinkle the veggies with salt, and toss to combine and evenly coat the salad. Add the olive oil and red wine vinegar, and gently toss to combine and evenly coat the salad. Allow the ingredients to rest about 10-15 minutes, on the counter at room temperature, to soften the onions and marinate the veggies.
Add the black pepper, basil, and cooled croutons. Gently toss the salad to combine the ingredients. Serve immeadiately.
Notes
*I like to peel the cucumber before slicing, but this is just my preference. The peel may be left on, if desired. This salad should be enjoyed the day it's made since the croutons will quickly soften due to the vinegar dressing.