Heat 4 tbsp vegetable oil or butter in a pan over medium heat. Add 2–3 finely chopped garlic cloves and sauté until fragrant. Stir in 1 finely chopped large red onion and cook until golden brown. Add 200g canned chopped tomatoes and simmer until thickened. Add 600g diced meat and cook until browned, seasoning with salt. Mix 1 sachet (50g) Rogan Josh spice mix with 100ml water and stir it into the pan. Simmer for 5–7 minutes until thick and rich.