7 sheets filo (Phyllo) dough, thawed
5 tablespoons salted butter, melted
7 tablespoons grated parmesan cheese, divided
1 cup very thinly sliced onion
1 cup shredded fresh mozzarella cheese
8 Roma tomatoes, cut into 1/8-inch thick slices*
Thyme leaves or basil leaves, minced
Salt and freshly ground black pepper

* Cut tomatoes very thin so juices evaporate while baking or dough will be soggy. 

Preheat oven to 375 degrees F. Line a large cookie sheet with parchment paper and spray paper with cooking-oil spray (or brush lightly with vegetable oil).

Lay one (1) sheet filo (Phyllo) dough on paper and brush lightly with a little melted butter. Sprinkle all over with 1 tablespoon parmesan cheese. Repeat layering five (5) more times (with filo, butter, and parmesan cheese), pressing each sheet firmly so it sticks to sheet below. Lay the last filo sheet on top, brush with remaining melted butter, and sprinkle on remaining 1 tablespoon parmesan cheese.

Scatter onion slices across filo dough, top with mozzarella cheese, and arrange tomato slices in a single layer, overlapping slightly. Sprinkle with thyme or basil and salt and pepper to taste.

Bake until the filo is golden brown, approximately 30 to 35 minutes. Remove from oven and let cool 10 minutes, then serve.

Serves many as an appetizer - Makes about 20 (3-inch squares).