Place eggplant in a colander in layers and sprinkle salt between each layer. Let sit for 5 minutes, then rinse the eggplant and squeeze out all water between the palm of your hands. Set aside.
Puree chili and ginger in a small food processor. Heat oil in a saucepan and add onions, cook until translucent.
Stir in ginger and cook until onions start to brown. Add cumin, turmeric, coriander, and garam masala, and stir.
Add tomatoes and stir for a couple minutes.
Add eggplant, and season with salt and pepper. Reduce heat, cover saucepan, and simmer for 60 minutes, stirring often mixture becomes a puree. If mixture is becomes too dry, add a little bit of water.

2 large eggplants, peeled and diced
2 tomatoes peeled, seeded and finely diced
3 tablespoon oil
2 onions, finely chopped
1 small chili pepper
1 1.5-inch piece fresh ginger
1/2 teaspoon ground cumin
1 teaspoon turmeric
1/2 teaspoon ground coriander seeds
1 teaspoon garam masala
salt and pepper