Preheat oven to 350º

Make the cinnamon swirl by creaming butter, brown sugar, flour, cinnamon, and lemon juice together

Add apples and stir to combine and coat apples

Set aside

To make the cake, combine flour, baking powder, and salt and set aside

Beat butter and sugar together until light and fluffy

Beat in sour cream, vanilla, and eggs until fully combined

Stir in flour mixture

Spread into a greased or parchment lined 8x8 inch baking pan

Top with apple cinnamon mixture, and use a butterknife to swirl apples into cake batter. You want to encourage some of the batter to rise over the apples

Bake in preheated oven for 40 minutes, until the edges are golden, and the center doesn’t jiggle. If you can, use the toothpick test (insert a toothpick into the center of the cake. If it comes out clean, it’s done), but this may be difficult because of the apple swirl

Remove from oven and let cool

While cake cool, whisk icing ingredients together, and drizzle icing over cake