Preheat oven to 180 C / Gas 4. Lightly grease a large baking dish.
Heat a large pan over medium-high heat. Cook and stir beef mince and onion in the hot pan until beef is completely browned, 5 to 7 minutes.
Stir tomato passata, black beans, chopped tomatoes, sweetcorn and chopped green chillies into the beef mixture; season with chilli powder, cumin, garlic, oregano and chilli flakes. Reduce heat to low and simmer for 5 minutes.
Spread 1/2 a ladle of the beef mince into the bottom of the prepared baking dish; top with 3 tortillas, overlapping as needed. Spread one ladle of the beef mince over the tortillas. Sprinkle some of the grated cheese over mince layer. Finish with layers of remaining tortillas, mince and grated cheese, respectively.
Bake in preheated oven until heated throughout and the cheese is melted, about 15 minutes. Cool 5 minutes before serving.