Preheat the oven to 425 degrees. Dice the tomatoes and onion and chop the basil.
In a large bowl, add the diced tomatoes and 1 teaspoon salt. Toss the tomatoes and set them aside.
Cube the baguette. Drizzle the baguette with olive oil and roast in the oven for 10 minutes. You want the baguette to be crunchy but still have a slight softness to it.
To assemble the salad, add the baguette, tomatoes, red onion and basil to a bowl and toss to combine.
For the dressing, combine all ingredients into a small mixing bowl and whisk until emulsified. Drizzle over salad.
Refrigerate the salad for 20 minutes to allow the bread to soak up the tomato juices and oil from the dressing.
Serve cold and enjoy!
Notes
Salting the tomatoes is an important and crucial step that shouldn't be missed. When salting the tomatoes, it helps to draw out the juices of the tomatoes giving it a better, brighter flavor.
Don't skip toasting the bread in the oven. This is important to avoiding terribly soggy panzanella. Even if you use day-old bread which hardens on its own, it is still important to cut it in cubes and toast it in the oven for a few minutes-just enough for the edges to get crusty, while the inside gets firm but remains chewy.
Allow the panzanella to sit for a bit before serving. This is an important step that shouldn't be missed. It only needs to sit for about 20-30 minutes to really let the juices of the tomatoes and dressing penetrate the bread.