• Grease very well a 7 inch baking pan and line it with a circle of parchment paper.
• In a mixing bowl whisk together the 1 1/2 cup all-purpose flour, 3/4 cup caster sugar and 2 teaspoons baking powder. Add the 2 large eggs and 1 teaspoon pure vanilla extract , and stir gently.
• The mixture will be thick. Add 1/3 cup vegetable oil and the 1/2 cup milk and continue whisking until the mixture becomes smooth.
• Add the 1 cup ground walnuts and whisk gently to absorb. Don’t overmix!
• Pour the batter into the prepared pan. Place the pan into the basket of the air fryer.
• Bake the cake for about 40 minutes at 340º F or until a wooden skewer inserted in several places comes out clean. Check after at about 32-35 minutes and continue baking if it is not done yet.
• Let the cake cool completely before assembling it. The frosting is optional: it is perfectly tasty also plain.

To Frost And Assemble:

• Using an electric mixer, beat together the 1/2 cup unsalted butter, 1/2 cup ground walnuts and 1/2 cup icing sugar in a large bowl, until fluffy.
• Gradually add the 3 tablespoons milk and continue mixing at high speed until the frosting increases its volume a bit and becomes even fluffier - about 2-3 minutes.
• Using a serrated knife, trim the top of the cake to make it even. You can use this part for decoration or eat it right away.
• Cut horizontally the cake into two layers. Place one on a serving plate and spread about ⅓ to ½ of the frosting on top. Place the second layer. Cover the cake all around with the remaining frosting.
• Optionally preserve 1 tablespoon of the frosting and mix it with some of the trimmed part of the cake top, broken into crumbs. Make small balls out of the mixture: truffles that you can use for decoration.
• Refrigetate until ready for serving.