Preheat your oven to 425ºF.
Peel eggplant skin in strips and cut in eggplant in half.
Brush eggplants all over with olive oil. Season with 1/2 teaspoon salt.
Roast eggplants till soft but no too mushy - about 15-20 minutes.
While the eggplants are roasting heat 2 tbs of olive oil in a large pan over a low heat. Add the sliced onion and spread across the base of the pan. Sauté the onions stirring frequently until they begin to caramelize (about 10-15 minutes). At that point, add the sliced garlic and cook until the onions reach a golden brown color. (another 3-4 minutes).
Add the diced tomatoes a quarter cup of water, season with cumin and oregano and bring stuffing to a simmer. Cook for a few of minutes until most of the water evaporates. The stuffing should be thick and firm.
Check eggplants. The centers should be soft. Remove from oven and with the back of a soup spoon gently press down on the cooked flesh and make a trough for the stuffing. With a spatula and tongs, turn the eggplants on their side to drain any liquid.
Distribute the filling equally among the eggplant halves.
Garnish with parsley or mint and toasted pine nuts (optional). Drizzle a little olive oil and serve at room temperature or refrigerate overnight.