Caramelized Onion Tart - cooking recipe

Ingredients

3 lb. large sweet onions, sliced
1 tsp. salt
1/2 c. shredded Parmesan cheese
2 Tbsp. olive oil
1/2 (17 1/4 oz.) pkg. frozen puff pastry sheets
fresh rosemary sprigs

Preparation

Thaw puff pastry at room temperature.
Cook onions in hot oil in a large skillet over low heat, stirring often, 30 to 35 minutes or until onion is caramel colored.
Stir in salt and set mixture aside.