Cabbage with fennel and onions

1 head cabbage, shredded
2 1/2 onions, peeled and sliced into half circles
1/2 cup oil
5 fenugreek seeds
1/2 tsp cumin seeds
1/4 tsp mustard seeds
1/2 tsp fennel seeds
2 garlic cloves, peeled and chopped
1 1/2 inch piece of ginger, peeled and chopped
1 tomato, ripe or canned, peeled and chopped
1/2 tsp turmeric
1 long hot green chili or 1/2 jalapeno, thinly sliced
1 tsp salt
1 tsp garam masala
1 tbsp lemon juice

Heat half the oil, add seeds. As they sizzle and change color (~30 seconds), add 2 sliced onions. Fry over medium for about 3 minutes. Add cabbage, stir, cover, lower heat, cook for 15 minutes.
Meanwhile, blend 1/2 onion, blend it with ginger, garlic, and tomato in a blender until pastelike.
Heat the other half of the oil, add blended paste, turmeric, and chili. Fry, stirring, for 8-10 minutes, adding a little water if necessary to prevent sticking. Add to the cabbage, with salt, garam masala, and lemon juice.

Source: Madhur Jaffrey's Spice Kitchen