Preheat the oven to 190°C. Line the bottom of a 9-inch, round cake tin with baking parchment and lightly grease the parchment and the sides of the tin.
Prepare the topping by bringing the sugar and water to a boil in a wide pan. Reduce to a simmer, gently place the orange slices in the pan, pat them down gently and cook for 10-15 min. Then very gently remove them from the syrup and drain on a plate.
Cut the orange into large chunks, remove and seeds and liquidise in the food processor or blender to a fine puree.
Whisk the flour, soda bicarb, salt and almond flour in a bowl.
In another bowl, whisk together the oil, sugar, eggs and orange puree. Fold in the dry mixture taking care not to overmix.
Arrange the drained orange slices to completely cover the bottom of the prepared tin and pour the batter over them. Tap the tin a couple of times to remove any air bubbles. Bake for 30 min or till a skewer inserted into the cake comes out clean.
Remove the tin from the oven and allow it to cool for 20 mins. Then use a toothpick to gently prick the cake all over and slowly pour the brandy evenly all over the cake.
Invert a plate or cake stand over the tin and very gently overturn to unmold the cake. The orange slices should be baked onto the top of the cake. Cool the cake fully before slicing.