To Make the Cake

• Preheat the oven to 350°F. Grease and line a 9 by 9-inch cake pan with parchment paper and set aside.
• In a medium mixing bowl, toss all of the apple cinnamon filling ingredients together and set aside.
• In a large bowl with a hand mixer (or in a stand mixer with the paddle attachment), mix together the butter and sugar until light and fluffy (2 to 3 minutes).
• Add in the eggs, allowing each to incorporate before adding in the next. Mix until combined. Add the vanilla. Mix until smooth.
• Stop the mixer and sift in half of the flour, baking powder, salt, and baking soda. Mix on low speed until incorporated.
• With the mixer on low speed, stream in the buttercream and mix to combined.
• Add the remaining flour and mix until smooth.
• Scrape half of the batter into the prepared pan. Smooth it out with an offset spatula.
• Spoon half of the apple filling on top.
• Dollop the remaining cake batter on top of the apples and gently smooth out.
• Add the remaining apple filling evenly over the top of the cake.
• Bake the cake for 40 to 45 minutes, or until golden on top and a toothpick inserted into the center comes out clean or with a few moist crumbs.
• Mix all of the ingredients together for the glaze until smooth and pourable.
• Drizzle the glaze over the top of the cake. Allow the cake to cool slightly before slicing. Serve at room temperture.