Preheat your oven to 400°F.
In a large bowl, combine the ground beef, breadcrumbs, green onions, soy sauce, sesame oil, brown sugar, garlic powder, ginger powder, black pepper, red pepper flakes (if using), and egg. Mix until just combined, being careful not to overmix.
Using your hands, shape the mixture into meatballs about 1 inch in diameter and place them on a baking sheet lined with parchment paper.
Bake for 15-20 minutes or until the meatballs are cooked through and browned.
While the meatballs are baking, prepare the spicy mayo dip by whisking together the mayonnaise, Sriracha, lime juice, and garlic powder until smooth.
Once the meatballs are done, remove them from the oven and let them cool for a few minutes before serving.
Serve the meatballs warm with the spicy mayo dip on the side.