In a saucepot on medium-low heat, add the pears, brown sugar, cinnamon, nutmeg and salt and stir to combine. Add the apple cider and simmer, partially covered, until the pears are tender and the juices are starting to thicken a bit, about 10 minutes. Then add the butter and lemon juice and cook about 5 minutes more. Pour into a bowl and set aside. (This can be made up to 2 days in advance, covered & refrigerated.

Thaw the sheet of puff pastry for about 30 minutes until no longer frozen. (Be careful not to let it get too soft.)

Preheat oven to 400F/ 200C.

Roll the puff pastry out, ever-so-slightly, between two pieces of parchment paper into a rectangle a tad larger than the original size. Remove the top piece of parchment and place the bottom parchment with the pastry on a large baking tray. (If the apples aren't sliced yet, put the puff pastry in the fridge while you prepare the apples.)

Drizzle the apple slices with lemon juice to help them from browning.

Spread the cooled pear compote in an even layer on the puff pastry, leaving about an inch border all around.

Then arrange the apple slices over the pear compote, overlapping slightly and fanning them out as you go, making sure to keep the inch border empty.

Brush the apples all over generously with the melted butter. Then sprinkle the apples evenly with the granulated sugar. (If you find you need a little more butter or sugar, no problemo.)

Bake for about 25-30 minutes or until the apples are tender and the pastry is puffed and golden brown.

Let the tart cool just slightly over a wire rack. If brushing with apricot jam for a glossy look on top, combine a few tablespoons of the jam with a little water and heat in a small saucepan, stirring until smooth. Then brush the still warm tart with the jam glaze. You can also just sprinkle powdered sugar all over the tart for an equally beautiful look. (I did a little of both- brushed the apples with the jam glaze and dusted the edges with a little powdered sugar.

Enjoy warm or at room temperature.