Make the tart dough by combining flour, salt, and sugar in either a mixing bowl or a food processor.
Add your butter either by hand (crumbling the cold butter into the flour until it your butter is broken down into smaller than pea size chunks or it resembles sand) or in the food processor (add your butter and pulse until the mixture resembles sand).
Add ice water (or just very cold water) and pulse or combine by hand until the dough starts to stick together. It’s okay if it’s still a little crumbly, but if it’s not coming together at all, add as many tablespoons of ice water until the dough comes together.
Wrap up your dough in plastic wrap and chill for at least 30 minutes. Towards the end of the resting time, preheat the oven to 190 °C or 375 °F
Prepare the marzipan filling by combining almond flour, powdered sugar, egg whites, and almond extract in a bowl until it forms a smooth paste. You can also combine in a food processor!
Right before the dough is done resting, thinly slice your apples and add them to a mixing bowl with brown sugar, cinnamon, lemon juice, pinch of salt, and vanilla bean paste/vanilla extract. Set aside until ready to use.
After the dough has rested, roll out into a 12" circle, about ⅛" to ¼" thick. We used a 10" tart pan for this recipe!
Prepare a tart pan by buttering the sides and the bottom and adding a piece of parchment paper to the bottom.
Roll the dough onto the rolling pin and transfer to the tart pan by unrolling it over the tart pan.
Lower the dough into the edge of the pan. Press down the corners gently, trying not to stretch the dough. If you need to patch any holes or add more dough to the edges to fill the fluted edge, just press any excess dough onto the hole or thin edge.
Clean up the edges by removing any excess dough by running a knife along the edge.
Put the tart in the freezer for about 5 minutes to cool down the butter in the dough from working with it.
Add marzipan filling to the tart, spreading it evenly across the base.
Arrange the sliced apples across the top of the tart in whatever pattern you like! We like to arrange them in a circular pattern, starting from the outside in, to create a rose.
For this pattern, overlap each slice halfway with the previous slice (the rounded edge of the piece of apple facing upwards).
Continue arranging the slices around in circles until you get to the very center.
Bake the tart for 35-45 minutes.
Remove from the oven and let the tart cool.
Once it has cooled, you can remove the edge of the pan. Cut into slices, top with whipped cream or ice cream, and enjoy!