Preheat oven to 180°C/356°F (vent oven 160° / 320°F).
In a large bowl, crack eggs (discard shelves), add granulated sugar and with an electric mixer mix about 8 minutes, until the eggs and sugar are thoroughly combined in a light and fluffy foamy mix.
While the eggs are being beaten, grate orange zest and squeeze juice. Add both to foamy egg mixture, then add also olive oil and mix another minute to combine.
In a separate bowl, combine flour and baking powder. Sift on egg mixture and fold in gently with a spatula by hand.
Cover the bottom of a round baking tin (fi 22 cm / 8-9 inches) with baking paper, and grease the sides with a bit of oil, then dust lightly with flour to prevent sticking. Pour dough into baking tin and place in preheated oven to bake for about 35-40 minutes. Check with toothpick when your cake is baked.
Remove baked cake from oven, take out of the baking tin and place on a rack to cool down. Once cooled, dust with confectioners sugar to decorate and serve.
6. Ohlajen kolač posuj s sladkorjem v prahu in postrezi.