Upside Down Potato & Onion Tart

The onions caramelize while the potatoes are cooking and when you turn them out of the pan they are gorgeous on the plate. The flavor combination is really heavenly. It's a great side dish or accompaniment for steak and roasts. From Hizzoner's Deli. Enjoy!

• Ready In: 1 hr 5 mins
• Yields: 1 tart

Ingredients

• 2 1⁄2 tablespoons butter
• 12  sprigs thyme, strip the leaves from the stems
• 1  large onion, sliced somewhat thickly (a tad more than 1/4 inch thick)
• 1  lb  waxy  red potatoes, washed and very thinly sliced
• 2  tablespoons olive oil
• 1⁄2 cup  grated gruyere cheese
• 1⁄2 cup  crumbled feta cheese
• 1  cup  grated mozzarella cheese
•  sea  salt and black pepper

Directions

1. Preheat oven to 400*F.
2. Melt the butter in a 9-10 inch ovenproof frying pan (cast iron is great) over medium heat. Add the thyme and onion and cook for 5 minutes. Spread out evenly in the pan.
3. Place the potato, oil, cheeses, salt and pepper in a bowl and toss to combine.
4. Top the onion with the potato mixture, spreading out evenly over the onions, and bake for 45 minutes or until golden brown and cooked through. Turn upside down to serve.
5. Note: For an extra cheesy tart, double the amount of mozzarella.