Heat vegetable oil in a large pot over medium-high heat and brown beef chunks on all sides, working in batches if needed. Remove and set aside.
Add onion to the pot and sauté until softened, about 5 minutes, then add garlic and ginger, cooking for 1 minute until fragrant.
Stir in curry powder and cook for 30 seconds, then add beef broth, coconut milk, fish sauce, and brown sugar, stirring to combine.
Return beef to the pot along with carrots, bring to a boil, then reduce heat to low and simmer covered for 75 minutes until beef is tender.
Add red bell pepper and cook for an additional 10 minutes until peppers are tender but still vibrant.
Serve over steamed rice and garnish with fresh cilantro.