Falafel-Spiced Tomatoes and Chickpeas on Flatbread

Name: Falafel-Spiced Tomatoes and Chickpeas on Flatbread
Cuisine: Middle Eastern
Ingredients: 2 garlic cloves, finely chopped; 1 teaspoon sumac; ½ teaspoon crushed red pepper flakes; ½ teaspoon ground coriander; ½ teaspoon ground cumin; 1 teaspoon kosher salt, plus more; 2 large heirloom tomatoes, any color, thinly sliced; 1 15.5-ounce can chickpeas, rinsed; 2 tablespoons red wine vinegar; Freshly ground black pepper; 1 small shallot, thinly sliced; ½ cup parsley leaves with tender stems; 3 tablespoons olive oil; 1 Persian cucumber, peeled, chopped; ¾ cup plain yogurt; ½ cup coarsely chopped fresh mint; ½ cup coarsely chopped fresh parsley; Hot sauce; Kosher salt and freshly ground black pepper; ¾ teaspoon baking powder; ½ teaspoon sugar; 2 cups all-purpose flour, plus more for surface; 2 teaspoons kosher salt, plus more; 1 cup plain yogurt; 4 tablespoons olive oil, plus more for drizzling; Sumac, a tart, citrusy spice, can be found at Middle Eastern markets and specialty foods stores