Preheat the oven to 425 degrees F. Line a baking sheet with parchment paper.
Halve the eggplant, then use a paring knife to cut vertical and horizontal slits into the flesh about 3/4-inch apart. (You want to create crosshatches across the whole surface without piercing the skin on the other side.) Place the halves on the lined baking sheet flesh-side up.
Spread a tablespoon of olive oil over each of the halves, then sprinkle both with the Italian seasoning, salt, pepper and garlic powder. Roast until the eggplant is softened and golden brown on top, 15 to 20 minutes. Remove the eggplant from the oven and spread 1/4 cup marinara on each half, then top with the cheeses. Return to the oven and bake until the cheese is golden and bubbling, another 8 to 10 minutes. Allow to cool slightly before serving.