Step 1: Place the whole oranges in a large pot and cover with water. Bring to a boil, then reduce heat and simmer for 2 hours until very soft. Drain and let cool.
Step 2: Preheat your oven to 350°F (175°C) and grease a 9-inch springform pan.
Step 3: Roughly chop the cooled oranges (skin and all) and remove any stray seeds. Pulse the oranges and dates in a food processor until a smooth paste forms.
Step 4: In a large bowl, whisk the eggs and sugar together until pale and thick.
Step 5: Fold in the orange-date puree and vanilla extract into the egg mixture.
Step 6: Stir in the almond meal, baking powder, and salt until just combined.
Step 7: Pour the batter into the prepared pan and bake for 45-55 minutes, or until a skewer comes out clean.
Step 8: Allow the cake to cool completely in the pan before removing and dusting with powdered sugar.