With a knife or fork, prick eggplant and lay directly on the gas stovetop over a high flame. Roast, rotating occasionally with tongs until slightly softened and skin is evenly charred.
Cool to touch and peel skin. Gently rinse under cold, running water to rid of stray skin and coarsely chop the flesh.
In a pan over medium heat, heat oil. Add onions and tomatoes and cook until softened. Remove from pan and allow to cool.
In a bowl, lightly beat eggs. Add roasted eggplant and sauteed onions and tomatoes. Season with salt and pepper to taste and stir to combine.
Grease sides and bottom of an 8-inch cast-iron or an ovenproof skillet with nonstick cooking spray. Over medium heat, add egg mixture to skillet and gently pat-down
Cook for about 2 to 3 minutes or until eggs begin to set.
Remove from the stove and transfer to a 375 F oven. Continue to cook for about 10 minutes or until eggs are set and lightly browned.
Transfer onto a serving plate and cut into wedges.