Preheat oven to 160°C / 140°C fan / 325 °F / Gas Mark 3.
With your pan over a medium heat, add the coconut oil. When it’s nice and hot, add the mustard seeds, fennel seeds and curry leaves.
As the mustard seeds start to pop, add the diced onion and salt. Cook until the onion has softened - about 5 to 10 minutes.
Add the green chilli, garlic, ginger, the ground spices and tamarind. Cook through for a couple of minutes.
Add the chuck steak pieces and coat with the spicy onion mixture. Cook for 5 minutes, stirring occasionally.
Add the tomatoes and 250 ml water and stir.
Simmer on low a heat on the stove top or cook in the oven for 3 to 3 ½ hours until your beef is nice and tender.
Remove the lid for the last 20 minutes of cooking to reduce the curry sauce if required.