Preheat the oven to 350 degrees. Spray an 8-inch springform pan with cooking spray. Cut a circle of parchment paper to fit in the bottom of the pan and spray lightly with more cooking spray.

In a medium mixing bowl, whisk together the almond flour, baking powder, and salt.

In the bowl of an electric mixer, combine the eggs, ½ cup powdered sugar, honey, and vanilla. Beat on medium speed for 3 minutes. Turn the mixer off, add the flour mixture, and beat on low speed until mixed in. Add the marmalade and finish mixing by hand with a spatula to make sure everything is well combined. Pour into the prepared pan. Sprinkle the top with the slivered almonds and bake for 25-30 minutes or until a toothpick inserted into the center comes out clean. Let cool in the pan then transfer to a serving plate. Sprinkle the top with powdered sugar and serve.