Preheat oven to 350 degrees.
Add butter (or olive oil) to heavy nonstick pan and heat over medium high heat until melted and foamy.
Add shallot and garlic to pan and cook 2 minutes, until fragrant and soft, stirring occasionally to prevent burning.
When shallot is slightly browned and fragrant, add zucchini to pan and season well with salt, pepper, and herbs.
Sauteé until just softened and browned, another 3-5 minutes, stirring occasionally to prevent burning.
Season well with herbs, salt, and pepper.
When zucchini has browned, remove from heat.
Sprinkle parmesan over zucchini, toss to coat.
Stir in marinara sauce over zucchini and onions.
Layer slices of mozzarella over skillet.
Bake 20 minutes, until cheese is bubbling and melted.
Remove and top with fresh basil, if desired.
Serve immediately.