Wash and dry all produce. Heat broiler to high or oven to 500 degrees. Combine bulgur, stock concentrate, 11/4 cups water, and a pinch of salt in a small pot. Bring to a boil, reduce to a simmer, and cover. Cook until tender, 12-15 minutes. Remove from heat and keep covered.

Halve, peel, and cut onion into 1/2-inch wedges. Quarter tomato through stem end. Halve zucchini lengthwise and slice into 2-inch wedges. Toss veggies on a baking sheet with a large drizzle of olive oil, sumac, salt, and pepper. Broil (or roast) until softened and slightly charred, 10-12 minutes.

Lightly mix ground beef, panko, Middle Eastern spice blend, salt, and pepper in a medium bowl to combine. Gently pat into golf ball-sized meatballs with your hands.

Heat a drizzle of olive oil in a medium pan over medium-high heat. Add meatballs and cook to desired doneness, 6-10 minutes, turning to brown on all sides.

Finely chop parsley. Fluff bulgur with a fork, season with salt and pepper, and stir in half the parsley.

Divide bulgur between plates. Top with veggies and meatballs. Dollop with sour cream and garnish with remaining parsley.