Preheat your oven to 400°F / 200°C. Prick the eggplant all over with a fork, place it on a baking sheet, and roast for about 1 hour, or until it's completely soft and has collapsed.
Let it cool just enough to handle, then slice it open, scoop out the smoky pulp, and discard the skin. Give the pulp a coarse chop and drain away any excess liquid.
In a medium saucepan, heat the vegetable oil over medium heat.
Add the chopped onions and sauté until they become soft and translucent.
Stir in the grated ginger, garam masala, and cayenne pepper, cooking for another minute until fragrant.
Add the chopped tomato and cook until it just begins to soften.
Remove the pan from the heat.
Stir the chopped eggplant pulp, salt, creamy yogurt, and fresh cilantro into the saucepan with the onion-tomato mixture.
Mix everything together until well combined.
Taste and add more salt if you think it needs it.
Transfer the raita to a serving bowl, cover, and chill in the refrigerator for at least 1 hour to allow the flavors to meld together.
Serve cool.
