Preheat the oven to 325°F.

Heat the oil in a large, oven-safe pot over low heat. Add the sliced onion and cook for 5–7 minutes, stirring occasionally, until soft and lightly golden.

Stir in the curry paste along with about ½ cup of the coconut milk. Cook for 2–3 minutes, stirring constantly, until fragrant and slightly thickened.

Pour in the remaining coconut milk and the water. Stir until smooth and well combined.

Add the beef chunks, making sure they are mostly covered by the sauce. Cover with a lid and place the pot in the oven. Cook for about 2 hours, until the beef is very tender.

Carefully remove the pot from the oven. Stir in the potatoes, cover again, and return to the oven for another 30 minutes, until the potatoes are fork-tender.

Take the pot out of the oven and stir in the tamarind paste, brown sugar, and peanuts. Return the pot to the oven uncovered and cook for 20–30 minutes, allowing the sauce to thicken and deepen in flavor.

Remove the beef to a bowl and gently shred it using two forks. Return the shredded beef to the pot and stir to combine.

Stir in the lime juice and taste. Adjust sweetness or acidity as needed. Remove from heat and sprinkle with fresh cilantro.