Sweat onion and garlic in oil. Add potato and eggplant and stir fry until light brown.
Add spice mixture.
Add liquids, cover for 5 min and let simmer over low heat until potatoes are tended. Salt, pepper, and cayenne to taste.
Remove from heat, stir in tomatoes and cool.
Garnish with lemon wedge, cilantro, scallions.