Mix the kefta base

• Combine the onion, parsley, garlic, cumin, coriander, paprika, salt and pepper in a bowl.
• Work everything together so the flavors are evenly distributed before the meat goes in.

Add the meat and form the block

• Add the ground beef and mix until just combined.
• Press the mixture into a flat block on the sheet pan.
• Use a spatula to cut it into long kefta portions.

Add tomatoes and roast

• Scatter the quartered tomatoes around the kefta.
• Drizzle everything generously with olive oil.
• Roast until the kefta are cooked about 90% through.

Make the sumac onions

• Thinly slice the red onion.
• Toss with the sumac and a pinch of salt.

Make the harissa tahini

• Whisk the tahini with the harissa, grated garlic and lemon juice.
• Loosen with cold water until creamy and pourable.

Broil for caramelization

• Switch the oven to broil.
• Finish the kefta until the outside is caramelized.

Build the sandwiches

• Spoon the pan juices over the bread.
• Add the kefta, tomatoes, sumac onions and harissa tahini.
• Optionally toast the sandwich in a pan to seal it together.