Preheat the oven to 350°F with the oven rack in the middle. Either line a 9-inch springform pan with wax paper, or spray with cooking spray the entire pan to avoid the cake sticking.
In a large bowl (or in a stand mixer bowl), use an electric mixer on medium-high speed to beat the room temperature butter until creamy. Add the sugar, orange zest, and beat for 2 to 3 minutes until light and fluffy. Scrape the sides down with a silicone spatula. Add the eggs, one at a time, beating well after each one. Then beat in the amaretto liqueur.
To the cream mixture, add the almond flour, baking powder, and salt and mix until all are well incorporated.
Scrap the cake batter into a springform pan, and spread evenly. Bake for 35 to 38 minutes, until a toothpick inserted in the center of the cakes comes out with a few moist crumbs attached. This cake won't be a dry one!
At the last 10 minutes mark before the cake is done, squeeze the juice of the zested orange into a small saucepan, along with 2 tablespoons of sugar. Over medium heat, simmer the syrup until the sugar dissolves and thickens. I like using a metal frothing cup since it can stand the heat from the stove.
Once the cake is removed from the oven, poke several holes with a toothpick or skewer. Pour the thickened syrup over the cake, and use the back of a spoon the spread the syrup evenly.
BOOZY WHIPPED CREAMPlace a large metal bowl in the freezer while the cake rests. Before serving, remove the bowl from the freezer, add the heavy cream, confectioner's sugar, and bourbon (or Grand Marnier), and on medium speed, mix until soft peaks form.
Using a strainer, sprinkle more confectioner's sugar on top to cover those beautiful holes! Serve the cake with the boozy whipped cream, and enjoy!
Notes
DRIED ORANGE SLICESIn a 200° oven, cut orange slices, and place them on a sheet pan, and dry for 1 hour. The heat will slowly dry the orange slices. This could be done the night before or in the second oven. totally optional, but oh so pretty!