In a bowl, mix the flour, baking powder, cinnamon, and cloves. Coarsely chop the walnuts with a knife. Add 1 ½ cups of the walnuts to the flour mixture and mix. Avoid using a blender as it will turn the walnuts into a powder, making the cake dense. In another bowl, combine the sugar and orange zest, stirring to release the zest's essential oils and flavor the sugar.
In a mixing bowl, beat the sunflower oil and the flavored sugar until frothy. Gradually add spoonfuls of 1/3 of the flour mixture, alternating with the orange juice, and then add the remaining flour mixture.
Preheat the oven to 180°C (356°F) at the fan setting. Line a 24-25 cm round pan with non-stick greaseproof paper. To line the walls of the pan, fold the paper in quarters, then fold it again 2-3 times to form a triangle. Place the tip of the triangle in the center of the pan's base and measure up to the edge. Trim the excess paper with scissors. Make two small slits at the base of the triangle, then unfold the paper and fit it into the pan. This eliminates the need to oil and flour the pan.
Pour the batter into the prepared pan and sprinkle with the remaining ½ cup of coarsely chopped walnuts. Bake in the preheated oven for 55 minutes. Allow to cool before serving.