Cut the tomatoes in half crosswise and squeeze lightly to remove the seeds. With a serrated knife, dice the tomatoes and transfer to a strainer to drain. In a salad bowl, mix together the cucumber, greens, scallions, herbs, jalapenos, and capers. Add the tomatoes. To make the dressing, whisk together the olive oil, lemon juice, vinegar, lemon zest,and salt and pepper to taste. Pour over the salad and toss. Taste and adjust the seasoning. Refrigerate for 20 to 30 minutes to give the flavors time to meld. Sprinkle with sumac before serving if you like.