– 1/4 cup melted butter, cooled down a bit – 1/4 cup vegetable oil – 3 large eggs, close to room temperature – 1/2 cup milk, close to room temperature – 2 teaspoons lemon juice – 1 (15 ounce) box yellow cake mix (do not add the other ingredients listed on the box) – 1 cup fresh or frozen blueberries, rinsed and dried (I used frozen) – 3 tablespoons brown sugar (I used light brown sugar)