Preheat the oven: preheat the oven to 180°C / 350-375°F / Gas Mark 4-5.
Make the meatballs: add the beef mince, panko breadcrumbs, chilli powder, garlic powder, onion powder, cayenne pepper, paprika, coriander, cumin, salt, pepper and egg to a medium bowl. Use clean hands to mix together then portion and roll into meatballs with the palms of your hands. Repeat till the mixture is all mixed up.
Brown: add a little avocado oil to a fry pan, turn the heat to high and use tongs to place the meatballs into the pan. Brown the outsides of the meatballs, using tongs to rotate to the other side to ensure consistent browning.
Oven bake: spray a deep baking dish with a little oil then add the onion and sliced capsicums. Place the browned meatballs on top of the vegetables and then drizzle a little avocado oil over the contents of the baking dish. Place the tray into the oven on the middle shelf and allow the meatballs to cook for 15 to 20 minutes.
Serve: once cooked, remove the baking tray from the oven. Let sit for a couple of minutes. Then spoon the meatballs and vegetables into soft tortillas and provide lime wedges and yogurt sauce for eating.