INGREDIENTS
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7 sheets filo dough, thawed
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5 tablespoons unsalted butter, melted
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7 tablespoons grated parmesan cheese, divided
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1 cup very thinly sliced onion
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1 cup shredded mozzarella cheese
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8 Roma tomatoes, cut into 1/8-in.-thick slices
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1 tablespoon fresh thyme leaves
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Salt
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Freshly ground black pepper