Preheat the oven to 350°F. Make the caramel: In a saucepan, heat the sugar and 3 tablespoons water over medium heat until the sugar dissolves and turns a light amber color, occasionally scraping down the sides with a rubber spatula. Add the butter, salt, and liquor, stir, remove from the heat, and stir until smooth. Carefully pour into the bottom of a 9-inch round cake pan, rotating the pan to evenly distribute along the bottom. Let cool.

Decoratively arrange the orange slices, slightly overlapping, on top of the caramel to coat the entire bottom of the pan. Set aside.

Make the cake: Place the pistachios in a pan and toast until lightly browned, 5 to 10 minutes. Let cool, transfer to a food processor or spice grinder, and grind into a coarse meal. Set aside. Lower the oven temperature to 330°F.

Separate the eggs, putting the 7 yolks in one bowl, 2 of the egg whites in a second bowl, and the remaining 5 egg whites in a third bowl.

In a large mixing bowl, combine the honey, egg yolks, and 2 egg whites and mix well. Add the almond flour, 1⁄2 cup of the pistachio meal, the salt, orange zest, and liquor. Mix well and reserve.

In the bowl of a stand mixer fitted with a whisk or by hand, whisk the remaining 5 egg whites until bubbly. Add the sugar and whisk on high speed until soft peaks form. Working quickly, gently fold the meringue into the flour mixture in three stages. Pour enough cake batter onto the caramel in the prepared pan to just reach the rim.

Bake until the cake is firm to the touch and a toothpick inserted into the center comes out clean, 25 to 30 minutes. Let the cake rest for only 5 minutes, then carefully place a plate on top of the pan, hold them firmly together, and flip them over so the cake releases onto the plate. Rearrange the orange slices if needed and let rest at room temperature for at least 2 hours before cutting.