Twice Cooked Tomato Chutney with Cumin and Fennel

3 tablespoons vegetable oil
1/4 teaspoon each cumin seeds, fennel seeds, black mustard seeds, urad dal (black gram)
1/8 teaspoon fenugreek seeds
1 dried red chili, optional
1/2 cup curry leaves loosely packed
1 large onion (about 2 cups when diced)
8 pods garlic, peeled
6-8 (about 1 lb) ripe tomatoes, diced
1 teaspoon sambar powder

for tempering:
1/2 tablespoon vegetable oil
1/8 teaspoon each cumin seeds, fennel seeds, black mustard seeds, urad dal
a few curry leaves

Heat oil in a large wok. Add cumin, fennel, black mustard and urad dal. When the mustard seeds begin to pop, add fenugreek seeds, red chili if using, and curry leaves. Cook for about 30 seconds. Then add chopped onion and garlic. Cook on medium heat for 2 minutes. Add chopped tomatoes and cook on medium for about 15 minutes or till the tomatoes are completely soft.
Cool the chutney a little and then puree in a blender, along with sambar powder and 1/2 cup water till smooth. (Make sure to vent the blender lid slightly when blending hot stuff).
Wipe the wok, and heat oil for tempering. Add all tempering ingredients. When the mustard seeds splutter, reduce heat and carefully pour the blended chutney into the wok. Be very careful, the chutney may bubble and splatter. Add salt. Cover the wok and cook the chutney on medium-low for about 15 minutes, stirring occasionally. Serve with idli, dosa or pita bread.