Preheat the oven to 325F (160C), and grease and line the bottom of one 9-inch pan.
In a large bowl (or a bowl of a standing mixer) measure the sugar, then use a fork to run the zest into the sugar until the mixture is orange in color.
Beat in the eggs until you have a light and fluffy mixture, about 1 minute if using a mixer, or 2-3 minutes if using a whisk.
Pour in the melted butter and mix until incorporated then mix in the olive oil.
Mix in the sour cream and orange blossom water.
In a medium bowl, measure the flour and baking powder.
Add the flour mixture into the liquid mixture.
Pour the cake batter into the prepared pan and bake over the medium oven rack for 55-65 minutes.
The cake is ready when a cake tester, or a toothpick comes out from the center of the cake with a few moist crumbs.
Remove from the oven and allow the cake to cool in the pan for about 20 minutes before inverting it.