In a non-reactive bowl, combine the beef cubes, vindaloo paste, and malt vinegar. Marinate for at least 30 minutes.
Heat vegetable oil in a large heavy-bottomed pot or Dutch oven over medium-high heat.
Remove beef from marinade, reserving the liquid, and brown the beef in batches until seared on all sides. Remove beef and set aside.
Reduce heat to medium and add onions to the pot. Sauté for 8-10 minutes until golden brown.
Stir in the garlic, ginger, turmeric, cumin, and cayenne pepper. Cook for 1 minute until fragrant.
Add the browned beef, reserved marinade, beef stock, and brown sugar to the pot.
Bring the mixture to a boil, then reduce heat to low. Cover and simmer for 75 to 90 minutes, or until the beef is fork-tender.
Remove the lid and simmer for an additional 10 minutes to thicken the sauce if necessary. Season with salt to taste.