Preheat the oven to 400°F (200°C). Line a large baking sheet with parchment paper.
2. Step
Make the meatballs: In a medium bowl, mix together the ground beef, garlic powder, paprika, cayenne, black pepper, salt, scallions, panko bread crumbs, eggs, and orange zest until fully incorporated.
3. Step
Use a 1½-tablespoon cookie scoop to portion the meatballs onto the prepared baking sheet in rows of 4, leaving 1½ –2 inches of space between each meatball.
4. Step
Bake the meatballs for 20 minutes, until brown and cooked through.
5. Step
Meanwhile, make the teriyaki sauce: In a small saucepan over medium heat, combine the soy sauce, brown sugar, garlic, ginger, red pepper flakes, and black pepper. Bring to a gentle simmer and cook for 2 minutes.
6. Step
In a small bowl, mix together the cornstarch and water. Stir the slurry into the sauce and continue to simmer until thick enough to coat the back of a spoon, about 10 minutes.
7. Step
Remove the meatballs from the oven and, using a fork, transfer a few at a time into the sauce to coat, returning to the baking sheet between batches. Coat the meatballs in the sauce a second time, then transfer to a serving platter.
8. Step
Garnish with sesame seeds and sliced scallions. Serve warm.
