In a medium size saucepan over medium-high heat, heat the olive oil. Add the onions, cumin, mustard, fenugreek seeds, cinnamon, cloves and cardamom. Cook over medium heat, stirring for about one minute.
Add the garlic, turmeric, ginger, chilis and curry powder. Cook another minute.
Add the lentils, potato, water and salt. Stir and cook another minute.
Simmer for 40-50 minutes until both the potato and lentils are tender, adding more water as needed. Add tomatoes and cook another 10 minutes.
While the lentils cook, make the chutney by adding all the ingredients to a bowl and tossing thoroughly.
Serve the lentils with the curry.