Grease or line an 8- or 9-inch round springform pan with parchment paper. Preheat your oven to 350°F (175°C).
In a large bowl, combine the sugar and egg yolks (set the egg whites aside in a separate bowl). Beat the mixture with a hand mixer (or whisk vigorously) until it becomes light and foamy.
Mix in the orange zest, orange juice, vanilla extract, and olive oil. Beat for an additional 2 minutes until well combined.
Add the almond flour, baking powder, and salt to the bowl. Mix until the batter is smooth and fully combined.
Using a clean whisk or hand mixer, beat the egg whites in a separate bowl until stiff peaks form.
Gently fold the beaten egg whites into the cake batter using a spatula. Do this gradually and carefully to maintain the light, airy texture.
Pour the batter into the prepared springform pan and smooth the top with a spatula. Sprinkle the sliced almonds evenly over the surface.
Bake for 30–32 minutes until the cake is golden brown, and a toothpick inserted into the center comes out clean.
Let the cake cool in the pan for about 10 minutes, then carefully release it from the springform pan. Once completely cooled, dust with powdered sugar if desired.
Notes
Ensure the eggs, orange, and olive oil are at room temperature. This helps the batter mix evenly and ensures the cake rises properly.
Use finely ground almond flour for a smoother batter and a finer cake texture. A coarser almond meal may lead to a heavier cake.
Freshly squeezed orange juice and freshly grated zest will give the cake a vibrant, aromatic citrus flavor. Avoid prepackaged orange juice for the best results.
If you don’t have tapioca flour, arrowroot powder or cornstarch can be used in its place to maintain the cake's structure.
Choose a good-quality extra virgin olive oil with a mild flavor. A strong, peppery olive oil may overpower the cake.
Let the cake cool fully before removing it from the pan or dusting it with powdered sugar. This ensures it firms up properly and doesn’t crumble.