Seville Orange (Bigarade) Cake Recipe No electric beaters

This cake recipe doesn't need any electric beaters, very easy to prepare and the result is surprisingly moussey, light and absolutely flavorful! 

Ingredients
1 big bigarade fresh juice about 1/3 cup + 2 tbsp of granulated white sugar
1 tsp bigarade zest 
85g of soften salted butter or no trans-fat margarine
2½ cup of granulated white sugar
3 medium eggs
1 cup plain flour +1 cup cake flour (1 cup flour less 1 tbsp, add 1 tbsp cornflour and sift) both sifted set aside. 
2 tsp baking powder

Method
Grease a 8" x 5" baking pan and line with parchment paper. Brush some margarine on the parchment paper and dust with flour. 
In a recipient, mix butter and granulated white sugar until crumbly. Add the eggs, mix until fluffy and then add the zest. Mix well, set aside. 
Now place a sifter on top of the yolk mixture bowl, add the sifted plain flour and cake flour. Sift half of the flour, add the baking powder. And sift all the remaining flour. 
Fold the flour with the yolk mixture until combined. 
Add 1 tbsp of vanilla essence and 1/3 cup of fresh bigarade juice. Fold in the batter until no liquid is visible. The batter will be smooth. Pour into your prepared pan. 
Place your oven rack in the middle, fill with boiling water, place your batter pan in the center. Waterbath for 55 minutes to 1 hour on 155 degrees C. Check with toothpick if the cake is done. 
The top cake must be dark brown. Let cool completely. Run a knife around the edge, place a plate on the top of the cake pan. Invert and remove the pan. Peel off the parchment paper. 
Sprinkle with icing sugar. 
Slice and serve.