Make the sauce: Heat the olive oil in a saucepan over medium-high heat. Add the onion and cook until soft, 5 to 7 minutes. Add the garlic powder, sumac and tomatoes and cook until thickened, about 20 minutes. Season with salt and pepper.
Make the pizza: Preheat the oven to 500 degrees F. Drizzle a rimmed baking sheet with 2 tablespoons olive oil and stretch the pizza dough to fill the pan (it doesn't have to be perfect since this is a rustic pizza). Brush the dough with olive oil and bake until just golden, 10 to 15 minutes.
Meanwhile, heat 2 tablespoons olive oil in a large skillet over medium-high heat. Add the eggplant and cumin, season with salt and pepper, and cook until the eggplant is tender, 7 to 10 minutes. Add the garlic and cook 5 more minutes. Meanwhile, heat the remaining 1 tablespoon olive oil in a separate skillet over medium heat. Add the red onion and cook, stirring occasionally, until caramelized, about 15 minutes.
Reduce the oven temperature to 450 degrees F. Top the crust with 1 cup sauce, the mozzarella, eggplant mixture, caramelized onion, olives, sun-dried tomatoes and feta. Return to the oven and cook until the cheese melts and the crust is golden brown, 15 to 20 more minutes, brushing the crust with olive oil halfway through.
Remove the pizza from the oven and brush the crust with olive oil again. Top the pizza with the mint.