Start by taking your cold ingredients—unsalted butter, eggs, and sour cream—out of the refrigerator and let them sit at room temperature for about 15 minutes. Preheat your oven to 350°F (175°C) and grease a 9x13 inch baking pan.

In a large mixing bowl, combine all-purpose flour, baking powder, salt, sugar, softened butter, sour cream, vegetable oil, eggs, and vanilla extract. Blend the ingredients until the batter is smooth and creamy, about 2-3 minutes.

In a separate bowl, mix together the brown sugar, cinnamon, and a pinch of nutmeg if desired. Stir until well combined and set aside.

Pour half of the prepared cake batter into the greased baking pan. Sprinkle two-thirds of your cinnamon filling mixture over the batter. Pour the remaining batter on top and smooth it out. Sprinkle the last of the cinnamon mixture on top and gently swirl everything together.

Bake the cake for 30-35 minutes, or until a toothpick inserted in the center comes out clean. The top should have a golden brown color.

Remove the cake from the oven and let it cool in the pan for about 10 minutes. Prepare the glaze by mixing powdered sugar, melted butter, honey, vanilla, and a little milk until smooth. Pour the glaze generously over the warm cake.