Heat 2 tbsp vegetable oil in a large pan with a lid.
Add 1 tsp cumin seeds and fry for a minute or two until fragrant.
Add a chopped onion and fry over a medium heat until soft. Stir often. Add the chopped ginger and garlic and stir. Cook for further minute.
Add ½ tsp turmeric, the chilli powder (if using) and the tin of chopped tomatoes. Stir well and bring to the boil.
Reduce the heat to a simmer and cook for 5-10 minutes until the tomato mixture has started to thicken.
Add the sliced carrots with 100ml coconut milk (or cold water) and stir. Bring to the boil, then reduce the heat to a simmer, cover with a lid and cook for 15 minutes or until the carrots are cooked through. Stir occasionally.
Add 1 tbsp garam masala and salt to taste. Stir well.