Preheat oven to 350º. Line a rimmed baking sheet with parchment paper.
In a large bowl, combine ciabatta, olive oil, and 1 teaspoon salt. Arrange in a single layer on prepared pan.
Bake until golden brown and crispy, 15 to 20 minutes. Let cool completely and transfer to a large bowl.
In a medium bowl, whisk together parsley, cilantro, vinegar, tarragon, green onion, honey, mustard, garlic, pepper, and remaining 1 teaspoon salt. Gradually add olive oil, whisking constantly, until fully combined. Pour half of dressing over bread and toss to combine.
Add salad greens, grape tomatoes, radishes, cucumbers, red onion, and feta; gently toss to combine. Top with tomato wedges and sunflower seeds and garnish with fresh basil, if desired. Serve with remaining dressing.
Recipe by Southern Lady Magazine at https://southernladymagazine.com/panzanella-salad/