1. Peel, core apples. Cut quarters lengthwise to make 1-inch (2.5 cm) thick wedges (8); set aside.
2. In 8-inch (20 cm) cast-iron skillet, melt butter/margarine over medium-high heat; add sugar and cook, stirring, until bubbly and just turning golden, about 2 minutes. Add maple syrup; cook, stirring, until sugar is dissolved. Remove from heat. Starting at edge of pan, arrange apples, flat side down, in concentric circles in syrup.
3. Simmer over medium-low heat, basting often, until apples begin to soften and syrup starts to thicken, about 10 minutes. Remove from heat; let stand for 5 minutes.
4. Meanwhile, on lightly floured surface, roll out pastry to 10-inch circle (use a 10″ plate to cut pastry).
5. Place pastry over apples, press pastry edge down between apples and pan; cut 4 small steam vents in centre.
6. Bake in centre of 425°F (220°C) oven until pastry is golden brown, about 35 minutes. Let stand for 7 minutes.
7. Wearing oven mitts, place a 9 inch pie plate over skillet, turn over to unmould onto pie plate (I have used small clamps to hold the two together before turning over). Replace any apples that may stick to pan and scrape out any sauce over apples. Let cool.