Preheat the oven to 425°F (220°C).
Season the zucchini: Toss sliced zucchini with 2 tablespoons olive oil, garlic powder, paprika, salt, and black pepper. Spread on a parchment-lined baking sheet in a single layer.
Roast for 20–25 minutes, flipping once, until golden and slightly crisp around the edges. Let cool slightly.
Toast the bread: While the zucchini roasts, toss cubed bread with a drizzle of olive oil and toast in the oven for 10–15 minutes, until golden and crunchy.
Make the vinaigrette: In a small bowl, whisk together red wine vinegar, 2 tablespoons olive oil, minced garlic (if using), a pinch of salt, and pepper.
Assemble the salad: In a large bowl, combine roasted zucchini, toasted bread, halved cherry tomatoes, red onion, and basil. Drizzle with vinaigrette and toss gently.
Let it sit for 10–15 minutes so the flavors meld and the bread absorbs some dressing.
Serve at room temperature, optionally topped with shaved Parmigiano or crumbled feta.