Preheat oven to 400°F and line a baking sheet with parchment paper.
Brush both sides of the eggplant slices lightly with olive oil and season with salt and pepper.
Bake for 15 minutes, flipping halfway through, until eggplant is tender and slightly golden.
Remove from the oven and spoon marinara sauce on top of each slice.
Sprinkle with mozzarella, Parmesan, oregano, and garlic powder.
Add any extra toppings you like.
Return to oven and bake for another 8–10 minutes until cheese is melted and bubbly.
Serve warm, garnished with fresh basil if desired.