Cut the beef chuck into 2-inch cubes and place them in a large mixing bowl. Sprinkle with salt and black pepper, then toss gently to coat the beef thoroughly. Set it aside while you prepare the other ingredients.

In a large skillet over medium-high heat, add the neutral oil. Once hot, add the seasoned beef and sauté for about 6 minutes or until it's browned on all sides. Transfer it to a plate and set aside.

Lower the heat to medium and add the chopped onion to the skillet. Cook for about 15 minutes, stirring often, until they turn golden brown and caramelized.

Stir in the minced garlic and let everything cook together for an additional 2 minutes until fragrant.

Mix in the spices: garam masala, cumin, paprika, turmeric, ground mustard, cayenne, ground ginger, and cinnamon. Cook this mix for a minute to bring out those lovely flavors.

Add the tomato paste and stir until everything is combined.

Pour the apple cider vinegar into the skillet to deglaze it, making sure to scrape up any tasty bits stuck to the bottom. Let it cook for 2 to 3 minutes, stirring constantly.

Bring in the beef stock and gently stir it all together. Add the beef back into the skillet and cook over medium heat until it starts to bubble.

When it starts boiling, reduce the heat to medium-low, cover, and let it simmer for about 60 minutes. Stir occasionally and flip the beef as needed. If the sauce thickens too much, you can add more beef stock to adjust the consistency.

Once the beef is tender and the sauce has thickened nicely, taste it and adjust the salt. If the vinegar flavor is too strong, mix in a bit of brown sugar and let it simmer for another 2 to 3 minutes.

Finally, serve your beef vindaloo over the basmati rice with warmed naan and a dollop of plain Greek yogurt if desired.