Prep the beef: Pat the beef dry and season generously with salt and pepper. Dry beef sears better and builds more flavor.
Sauté aromatics: Set the Instant Pot to Sauté (High). Add oil. Sauté onion 2 to 3 minutes until lightly golden. Add garlic, ginger, and lemongrass; cook 30 seconds until fragrant.
Sear the beef: Add half the beef in a single layer. Sear 2 to 3 minutes per side until browned. Remove and repeat with remaining beef. Don’t crowd the pot.
Bloom the spices: Return all beef to the pot. Stir in tomato paste, annatto (or paprika), five-spice, star anise, cinnamon stick, and bay leaf. Cook 1 minute to coat and bloom the spices.
Build the broth: Add beef broth, fish sauce, soy sauce, and brown sugar. Scrape the bottom with a wooden spoon to release browned bits. The liquid should just cover the beef. Adjust with a splash more broth if needed.
Pressure cook: Cancel Sauté. Lock the lid, set valve to Sealing, and cook on High Pressure for 35 minutes.
Quick release and add carrots: Quick release the pressure. Open carefully. Add carrot chunks and stir.
Pressure cook again: Cook on High Pressure for 3 minutes. Quick release. The carrots should be tender but not mushy.
Adjust and brighten: Remove star anise, cinnamon, bay leaf, and lemongrass stalks. Stir in lime juice. Taste and adjust salt, fish sauce, or sugar to balance savory and sweet.
Serve: Ladle into bowls. Top with cilantro, Thai basil, and scallions. Serve with crusty baguette for dipping, or over rice noodles or jasmine rice.
