01 - Preheat oven to 350°F. Grease an 8-inch square cake pan and line it with parchment paper.
02 - Sift flour, baking powder, and salt into a medium bowl. Set aside.
03 - In a large bowl, beat softened butter and sugar together until pale and fluffy. Add eggs one at a time, beating well after each addition. Stir in vanilla extract.
04 - Gradually add the sifted dry ingredients to the butter mixture in two additions, alternating with milk. Fold gently until just combined — avoid overmixing.
05 - Pour batter into the prepared pan and smooth the top with a spatula. Bake for 22–25 minutes, or until a toothpick inserted into the center comes out clean.
06 - Let the cake cool in the pan for 10 minutes, then invert onto a wire rack to cool completely.
07 - Once fully cooled, trim the edges and cut the cake into 12 even squares. Place squares in the freezer for 30 minutes to firm up for easier coating.
08 - Warm raspberry jam with hot water in a saucepan over low heat, stirring until smooth and pourable. Transfer to a shallow bowl.
09 - Spread desiccated coconut in a separate shallow bowl. Set up a wire rack over a baking sheet for draining.
10 - Dip each frozen cake square into the warm raspberry mixture, turning to coat all sides. Allow excess to drip off, then roll in desiccated coconut, pressing gently to adhere. Place on the wire rack.
11 - Let the coated lamingtons set at room temperature for at least 30 minutes before serving.