- With the rack in the middle position, preheat the oven to 425°F (220°C). Line a baking sheet with parchment paper.
- On a lightly floured work surface, roll out the dough to form a sheet ¼ inch (½ cm) thick, large enough to cut out two 8-inch (20 cm) circles. Place the dough circles on the baking sheet and prick lightly with a fork. Refrigerate.
- In a non-stick skillet over medium-high heat, soften the onions in the oil. Add the potatoes and brown over high heat. Add the garlic and cook for 1 minute. Season with salt and pepper. Let cool.
- In a bowl, combine the cheese, tomatoes and potato mixture. Adjust the seasoning. Spread the topping over the dough circles.
- Bake for 20 minutes or until the crust is golden.
- Cut the tarts into wedges and serve with sour cream, to taste. Serve with a salad, if desired. Also delicious as an hors d’oeuvre.
Cut out the dough circles using a plate or the bottom of a cake pan as a guide.