Step 1

Make the pastry dough: Cube the butter and set out at room temperature. In a separate large bowl whisk together the flour, sugar, and salt. Use your hands or a pastry cutter to work the butter into the flour until you see small, pea-sized pieces of butter. Stir in the sour cream with a fork. Form the dough into a ball and shape into a disk. Wrap with plastic wrap and refrigerate for 1 hour before rolling out. (See more instructions here: No Fail Sour Cream Pie Crust Recipe.)While waiting for the dough, prepare the pears and the caramel in steps 2 through 5.

Step 2

Prep the pears: Peel and halve the pears lengthwise. Reserve one pear half for the center of the tarte, and cut the remaining halves once more lengthwise.Core the pear quarters and the half. As you peel and cut the pears, place them in a bowl and sprinkle some lemon juice over them to keep them from turning brown.Sprinkle the pear pieces with 2 Tbsp sugar and toss to distribute the sugar and lemon juice over all the pears.

Step 3

Melt butter, add sugar to pan: Melt butter in cast iron pan on medium heat. Swirl the butter so that it coats the sides of the pan as well. Sprinkle 2/3 cup of sugar over the butter in an even layer. Remove the pan from heat.

Step 4

Arrange pears in pan: Place the single pear half, cut side up, in the center of the pan. Fan the remaining pear quarters, with the narrow side pointing toward the center, around the center pear half. Angle them as you go as to fit all of the pears in. Try to minimize any gaps.

Step 5

Cook gently until base is caramelized: Return the pan to medium heat and gently cook, without stirring the pears until the sugar butter mixture turns a deep caramel color, about 20 to 30 minutes. Remove from heat and place on a baking sheet pan.

Step 6

Sprinkle with nutmeg and ginger: Sprinkle the pears with grated nutmeg and minced candied ginger.

Step 7

Roll out dough and arrange over pears in pan: Preheat your oven to 375°F. Roll out the pastry dough to 11 inches if using a 9-inch cast iron pan and 12 inches if using a 10-inch pan. Place the pastry dough over the pears and gently tuck the edges inside the edge of the pan. Careful, the pan is still hot. I find using a fork helps to ease the dough inside the edges of the pan.

Step 8

Bake: Place the pan in the 375°F oven (on the baking sheet to catch any spillover) and reduce the heat to 350°F. Bake for 30 to 40 minutes until pastry is baked through and nicely browned. Remove from oven.

Step 9

Invert into pie pan: Place a rimmed serving dish or a pyrex or ceramic pie dish over the pan. Wearing thick, well insulated oven mitts or potholders, using two hands to hold the dish firmly over the pan, flip them over, releasing the tarte tatin to the plate. The caramel is hot and liquid-y and can easily spill, so take care and work quickly. Don't worry if some of the liquid spills out, just make sure to wear oven mitts (or long sleeves) and an apron to protect yourself as you do the flip.Flip the tarte over  while the tarte tatin is still hot, that way the caramel will not make the tarte stick to the pan as you invert it. The pears will likely have moved a bit in the flip-over, so rearrange them with a fork (they're hot!) so they form an attractive pattern.Let cool to room temperature before serving. Serve with a little vanilla ice cream or whipped cream.