• Peel and finely chop enough onion to measure ½ cup [1 cup].
• Cut a small corner from the ground lamb packaging 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 2 to 3 teaspoons oil until hot but not smoking. Add the onion, season with salt and pepper, and cook, stirring occasionally, until starting to soften, 2 to 3 minutes. Stir in the harissa spice blend and cook until fragrant, about 30 seconds.
Add the lamb, season with salt and pepper, and cook, stirring to break up the meat, until browned and almost cooked through, 4 to 5 minutes. Stir in ¼ cup [½ cup] water and cook until the liquid is thickened slightly and the lamb is cooked through, 1 to 2 minutes. Remove from the heat and season to taste with salt and pepper.
While the lamb cooks, prepare the garnishes and the yogurt sauce.

• Cut the tomatoes in half.
• Strip the mint leaves from the stems; coarsely chop or tear the leaves.

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

On the stovetop directly over a flame, or in a dry medium frying pan over medium heat, warm the flatbread, turning once, until lightly toasted, about 30 seconds per side. Alternatively, toast it in a toaster oven.
Place the flatbread on a cutting board. Spoon the lamb mixture evenly over the flatbread, leaving a ½-inch border around the edges. Cut into slices.

Transfer the lamb flatbread to individual plates, top with the tomatoes, and dollop with the sumac yogurt. Garnish with the mint and serve.