Preheat the oven to 325ºF (165ºC). Line the bottom of an 8-inch round cake pan with parchment paper. Grease and flour the insides.
In a medium-sized bowl, whisk together the flour, baking powder, baking soda & salt.
In a large bowl, beat the butter and sugar together, with an electric mixer at medium speed, until pale and fluffy. Add the honey and beat until well blended. Mix in the egg, egg yolk and vanilla extract in 3 separate additions, making sure each one is incorporated before adding the next.
In a small bowl, whisk the milk and sour cream together until well blended. On low speed, add the flour mixture into the batter in 2 additions, followed by half of the milk mixture after each addition. Beat just until smooth and combined. Do not over mix.
Transfer the batter to the cake pan. Smooth the top with a spatula. Bake until the cake is golden and a toothpick inserted into the center comes out clean, about 25-28 minutes. Let the cake cool in the pan for 10 minutes, then remove it from the pan and transfer it to a cooling rack. Brush the warm cake with Honey Butter Glaze.