Preheat oven to 425 degrees F. Heat olive oil in skillet over medium heat. Add onion and cook 3-4 minutes. Add garlic and sauté for another 2 minutes. Add marinara sauce and some fresh basil leaves. Mix well to combine.

Bring sauce to boil, then reduce to simmer. Add tomatoes, 1/4 cup of Parmesan cheese, salt and pepper. Mix well. Cook for 3-5 minutes, then remove from heat.

Slice zucchini thinly in hasselback style, about ¼-inch apart along full length of zucchini, stopping before cutting through. (Tip: Position zucchini between two chopsticks to prevent knife from slicing completely through.) Repeat for second zucchini.

In bowl, combine 1/4 cup Parmesan cheese and breadcrumbs. Mix well.

In baking dish, spread sauce and arrange zucchini side by side in center. Sprinkle breadcrumbs and Parmesan mixture over zucchini. Arrange mozzarella slices on top of sauce.

Bake 20 minutes, then broil 5 minutes until cheese is golden-brown. Top with fresh basil to serve.