Preheat the oven to 300°F.
Tear bread into large chunks and spread on a baking sheet.
Drizzle with olive oil, then sprinkle garlic powder, salt, and pepper. Toss well.
Bake for 10-15 minutes, flipping halfway, until golden and crisp. Let cool.
Make the vinaigrette. Combine all vinaigrette ingredients in a bowl or jar. Whisk or shake well. Let sit while prepping veggies.
Chop tomatoes and slice onion thin.
In a large bowl, toss together bread, tomatoes, onion, and mozzarella.
Pour vinaigrette over the top and gently toss. let sit for 15 minutes, then toss again.
Transfer to a serving platter and top with fresh basil.
Serve Immediately.