Start by blending the onion, garlic, ginger, turmeric, coriander, cumin, and chili powder until smooth, creating a spice paste. This will take about 2-3 minutes in a blender.

In a large Dutch oven, heat 3 tablespoons of vegetable oil over medium heat. Add the beef cubes and sear until browned on all sides, about 8-10 minutes.

Add the prepared spice paste to the pot and cook for 5 minutes, stirring continuously to release the aromas.

Pour in the coconut milk and beef broth. Add the bruised lemongrass stalks and torn kaffir lime leaves. Stir to combine.

Bring the liquid to a gentle simmer over low heat, then reduce heat to low and cover the pot.

Allow the dish to cook slowly for 2 to 3 hours, stirring occasionally to prevent sticking. Ensure the temperature remains low to enable tenderizing of the beef.

Check the seasoning and add 1 tablespoon of brown sugar and salt to taste. Continue simmering uncovered for another 15-30 minutes if you want the sauce to thicken further.

Remove from heat and let sit for 5 minutes to allow flavors to meld.

Serve hot, preferably over steamed rice or with side breads like roti or naan.