In a small bowl, combine sliced shallot with sumac, white wine vinegar, and ⅛ teaspoon kosher salt. Use your hands to mix and gently massage the mixture into the shallots. Set aside for 30 minutes to marinate.

Slice large tomatoes in half lengthwise and then into wedges. Place in a colander or sieve set over a large bowl. Lightly salt the tomatoes and let sit for 5 minutes as they release excess water. Discard the collected water, then wipe out the bowl.

Transfer tomatoes to the cleaned bowl and drizzle with 2 teaspoon champagne vinegar. Let marinate for another 5 minutes.

Add olive oil, tarragon, dill, a pinch of flaky salt, and freshly ground black pepper. Gently toss to combine.

Arrange tomatoes on a large serving platter. Spoon the sumac shallots evenly over the top.

Sprinkle with toasted pine nuts before serving.