Mix the Dry Ingredients: In a large bowl, sift the all-purpose flour and powdered sugar together.

Incorporate the Margarine: Add the cold, cubed margarine to the flour mixture. Using a pastry cutter or your hands, break down the margarine into the flour until the mixture resembles coarse breadcrumbs. Be sure not to overwork the dough to keep it light and flaky.

Add the Egg and Water: Beat the egg lightly and mix it into the flour mixture. Gradually add the ice-cold water, 1 tablespoon at a time, just until the dough starts to come together.

Form the Dough: Gently gather the dough into a ball, being careful not to knead it too much. Wrap it in plastic wrap and refrigerate for at least 30 minutes to allow it to chill.

Peel and Core the Apples: Peel the Granny Smith apples, remove the cores, and cut them into quarters. Set them aside.

Make the Caramel: In a heavy-bottomed oven-safe pan or cast iron skillet (about 9 inches in diameter), add the granulated sugar and heat over medium heat. Allow the sugar to melt without stirring—swirl the pan occasionally to ensure even melting.

Add Butter to the Caramel: Once the sugar has melted and turned a golden brown color, add the butter. Stir gently to combine and create a smooth, rich caramel sauce. Be careful, as the caramel is extremely hot.

Arrange the Apples: Once the butter has melted into the caramel, arrange the apple quarters in the skillet, rounded side down. Start from the outer edge of the pan and work your way inwards, creating a circular pattern. Pack the apples tightly, as they will shrink slightly while baking.

Cook the Apples: Let the apples cook in the caramel for about 15 minutes over medium heat, basting them occasionally with the caramel sauce to help them soften and absorb the flavor. After this, remove the skillet from the heat.

Prepare the Dough: Remove the chilled dough from the fridge. Lightly flour your work surface and roll out the dough into a circle about 1/8-inch thick, making sure it’s slightly larger than the diameter of the pan.

Place the Dough Over the Apples: Carefully place the rolled-out dough over the cooked apples, tucking the edges into the sides of the pan. Trim any excess dough if needed.

Bake the Tart: Preheat your oven to 375°F (190°C). Transfer the skillet to the preheated oven and bake for 25-30 minutes, or until the crust is golden and crispy.

Cool and Invert: Once baked, remove the skillet from the oven and let it cool for 10 minutes. To unmold the tart, place a large plate over the skillet and carefully flip it upside down. Be cautious of the hot caramel sauce as you invert it.

Slice and Serve: Allow the Tarte Tatin to cool for another 10 minutes before slicing. Serve warm, either on its own or with a dollop of whipped cream or a scoop of vanilla ice cream.

Enjoy your homemade Tarte Tatin, a French classic with perfectly caramelized apples and a tender, buttery crust!