Sauté the onion, garlic, and chilli pepper in the olive oil over medium heat for 2-3 minutes until softened.
Add the peeled tomatoes with their juice, tomato ketchup, salt, sugar, curry powder, paprika powder, and oregano. Cook over low heat for at least 1 hour.
While the sauce simmers, dice the steaks into roughly 2-3 cm cubes. Peel the onions and cut each into quarters or halves.
Cut the bacon into bite-sized pieces. Core the green pepper and cut into similar-sized pieces. Thread the meat cubes, onions, bacon, and green pepper onto kebab skewers in alternating order.
Heat oil in a large pan over medium-high heat. Fry the skewers in batches on all sides for roughly 2-3 minutes per batch. Lightly season with salt.
Season the tomato sauce with cayenne pepper and Worcestershire sauce. Place it in a large saucepan, add the fried skewers, and bake in a preheated oven at 175°C (350°F) for roughly 1 hour.