Preheat oven to 360º F/ 180º C. Line two 7 inch/ 18 cm baking tins with circles of parchment paper. Grease very well the tins.

In a bowl combine the flour, baking powder and salt. Mix very well. Optionally you can sift them all together (recommended).

In a large mixing bowl beat the eggs and the sugar with an electric mixer for 5 minutes. The mixture should at least double its volume.

Add the lemon zest or extract and the oil. Beat shortly to combine.

Using a rubber spatula gradually add the dry ingredients, alternating with the buttermilk. Make sure the flour is well absorbed in the batter and there are no lumps remaining.

Pour the batter into the prepared pans. Bake for about 30 minutes or until the tops are golden and a toothpick inserted in the centre of each comes out clean.

Let the bases cool until room temperature before preparing the frosting and assembling the cake. For best results refrigerate them for 3-4 hours or overnight.

In a large mixing bowl beat together the butter and the chocolate spread with an electric mixer until fluffy.

Gradually add the cocoa powder and the powdered sugar, mixed together. Beat with the mixer at medium speed until the dry ingredients are absorbed. Alternate with the milk or cream.

When all the ingredients are incorporated, switch to high speed. Beat for additional 1-2 minutes so the mixture becomes fluffier.

Using a long serrated knife cut horizontally the layers in two.

Place one layer on a serving plate. Spread about ¼ of the frosting on top.

Cover with another layer. Continue the process until using all layers. Spread on the top the remaining frosting. Spread gently around the cake, just to cover any holes between the layers.

Refrigerate for 4-5 hours or overnight. Decorate with chocolate, hazelnuts and/ or lemon zest before serving.