Place eggplant and zucchini in a colander over a plate; sprinkle with salt and toss.
Let stand for 30 minutes; rinse and drain well.
Cook pasta according to package directions. Meanwhile, in a large nonstick skillet, saute the eggplant, zucchini and onion in oil until tender.
Add the tomatoes, tomato paste, oregano, garlic powder, basil and pepper. Bring to a boil. Reduce heat; cook, uncovered, over medium-low heat for 3 minutes, stirring occasionally.
Drain pasta; place on an ovenproof platter. Top with vegetable mixture.
Sprinkle with mozzarella cheese. Broil 4-6 in. from the heat until cheese is melted.