Preheat the oven to 160°C/325°F. Grease a 13x9-inch pan generously with cooking spray and set aside.
Add brown sugar, cinnamon, and nutmeg to a small bowl. Mix thoroughly and set aside.
In a mixing bowl, cream the butter, oil, and sugar until fluffy and starts to look white – about 3 minutes. Add sour cream and mix for another minute.
Stir in the eggs, one at a time, beating the mixture well between each addition.
Sift the flour, baking powder, and salt into the batter. Then add the vanilla extract.
Stir well until everything is well combined. Scrape down the sides of the mixing bowl as you mix.
Pour half of the batter into the greased pan. Then sprinkle about ¾ of the sugar mix over the batter in the pan. Spread the remaining batter evenly over the sugar-cinnamon mixture.
Next, sprinkle the remaining cinnamon-sugar mixture on top of the cake. Make swirls with a spoon if desired.
Bake at 325°F/163℃ until a tester inserted into the center comes out clean – about 40 minutes.