Trim ends off lemongrass and cut into 3-inch pieces. Pound gently with a heavy object until bruised.
Mix lemongrass stalk, fish sauce, ginger, applesauce, curry powder, five-spice powder, and bay leaf in a large bowl. Add beef; mix until coated. Let marinate in the refrigerator, about 30 minutes.
Preheat oven to 300 degrees F (150 degrees C).
Drain excess marinade off beef, reserving lemongrass and bay leaf.
Melt ghee in a Dutch oven over medium-high heat. Cook beef in batches until browned, about 30 seconds per side. Transfer beef to a plate. Reduce heat to medium-low. Add onion; cook and stir until soft, about 5 minutes. Stir in tomatoes and salt. Simmer until thickened into a paste, 12 to 14 minutes.
Stir beef, reserved lemongrass, and bay leaf into the tomato paste. Increase heat to medium and cook, stirring often, until flavors combine, about 5 minutes. Increase heat to high. Add water and carrots; bring to a boil.
Cover and cook in the preheated oven until beef is tender, about 2 1/2 hours. Garnish with cilantro.