Steam or boil the potatoes until almost done. If they are big then cut them into manageable pieces.

Chop garlic. Saute garlic in oil with chillies, cumin, coriander, turmeric, chili powder, and salt for about 5 minutes.
Add tomatoes, and simmer 3-5 minutes until heated through.
Add the potatoes and a little water if necessary, cook 5 minutes, taste for seasoning.
Stir in the lemon juice, the reserved minced coriander.
You may double the amount of tomatoes depending on how much you have on hand because over time, the potatoes will absorb all the liquid.

500 gram waxy potatoes
1 small bunch fresh coriander
40 gram olive oil
2 large garlic cloves, peeled and chopped
2 small red chillies, seeded and chopped
1 teaspoon ground cumin
1.5 teaspoon ground coriander
1/4 teaspoon turmeric
1/4 teaspoon ground chilli powder (optional)
1/2 teaspoon salt
200 gram chopped tomatoes (canned or tetra box)
1/2 teaspoon lemon juice