• Peel the cucumber, if desired, and trim the ends; cut the cucumber in half lengthwise. Cut the halves lengthwise into ¼-inch-thick slices, then crosswise into enough ¼-inch pieces to measure ½ cup [1 cup].
• Strip the parsley leaves from the stems; coarsely chop the leaves.
• Cut the tomatoes in half; set aside for garnish.

In a small bowl, stir together the yogurt, cucumber, parsley, and 1 tablespoon [2 TBL] oil. Season to taste with salt and pepper.

• Cut a small corner from the ground lamb packages and drain off any excess liquid. Transfer to a plate; pat dry with a paper towel.

In a large frying pan over medium-high heat, warm 1 to 2 tablespoons oil until hot but not smoking. Add the lamb and harissa spice blend, season with salt and pepper, and cook, stirring to combine the seasonings and break up the meat, until browned and cooked through, 5 to 7 minutes. Transfer to a plate. Season to taste with salt and pepper. Wipe out the pan if using for the pita breads.
On the stovetop directly over a flame, or in the same pan used for the lamb over medium heat, warm the pita breads, turning once, until lightly toasted, about 30 seconds per side. Alternatively, toast them in a toaster.

Transfer the pita breads to individual plates and spoon on the lamb. Top with the spinach, tzatziki, and tomatoes and serve.