- 1 large shallot, thinly sliced
- 1/2 cup red wine vinegar
- Kosher salt, freshly ground pepper
- 3 1/2 pounds assorted ripe green heirloom tomatoes (such as Green Zebras), cut into wedges
- 1/2 cup extra-virgin olive oil
- 4 cups torn 1 1/2″ pieces white country bread, with crusts (about 1/2 of a 1-pound loaf)
- 2 garlic cloves, lightly crushed
- 3 tablespoons olive oil
- Kosher salt, freshly ground pepper
- 2 cups arugula, thick stems trimmed
- Combine shallot and vinegar in a small bowl; season with salt and pepper and toss to combine. Let stand 30 minutes.
- Meanwhile, place tomatoes on a large rimmed baking sheet; season with salt and let stand 15 minutes.
- Transfer 2 tablespoons vinegar from shallot mixture to a large bowl (reserve remaining vinegar with shallots). Whisking constantly, gradually add oil; whisk until combined. Season dressing with salt, pepper, and more vinegar from shallot mixture, if desired.
- Add tomatoes and their juices to dressing and gently toss to coat. Let tomato mixture stand at room temperature until tomatoes release more juices and soften slightly, about 1 hour.
- Meanwhile, preheat oven to 350°F. Combine bread and garlic on a large rimmed baking sheet and drizzle with oil; season with salt and pepper. Squeeze bread pieces lightly with your hands so they will evenly absorb oil and spread out in a single layer.
- Bake bread pieces, tossing occasionally, until crisp on the outside but still chewy in the center, 10-15 minutes. Let croutons cool slightly, then discard garlic.
- Add arugula and croutons to bowl with tomato mixture; season with salt and pepper and toss to combine. Drain pickled shallot. Serve panzanella topped with pickled shallot.