Chop ripe tomatoes into bite-sized pieces and sprinkle with kosher salt. Let sit for 15 minutes to extract juices.

In a large skillet, cook diced pancetta over medium heat for 5-7 minutes until crispy. Remove pancetta and set aside, keeping drippings in the pan.

Drizzle olive oil into the skillet with pancetta drippings, add cubed ciabatta, and toast for 5-7 minutes until golden brown.

In a small bowl, whisk together reserved tomato water, red wine vinegar, and Dijon mustard. Gradually add olive oil until emulsified. Season with salt and pepper.

In a large mixing bowl, combine toasted ciabatta, pancetta, cucumber, mozzarella, and herbs. Pour the dressing over and toss gently.

Let sit at room temperature for 30-60 minutes before serving to allow flavors to meld.