Preheat the oven to 350ºF (180ºC) and lightly spray the inside of a 10-cup Bundt pan with baking spray. Set aside.
In a large mixing bowl, combine the buttermilk, sugar, melted butter, vegetable oil, eggs, vanilla, lemon zest, and lemon juice. Use an electric hand mixer to mix everything together until smooth.
Use a fine mesh sieve to sift the cake & pastry flour, baking powder, and baking soda into the bowl. Add the salt. Switch to a rubber spatula or wooden spoon. Stir the cake batter together until the flour is just combined—a few streaks of flour are ok and the batter will look lumpy.
Use a measuring cup to scoop the batter evenly into the prepared Bundt pan, avoiding the center column. Use your spatula or spoon to lightly smooth the top of the batter before placing the cake tin in the preheated oven. Bake the cake for 37 to 40 minutes, or until the top springs back when lightly pressed with a finger, and the sides are pulling away from the tin.
Remove the cake from the oven and place the tin on a wire rack. Cool the cake for 10 minutes before turning it out of the tin onto the rack. Cool the cake completely before icing or glazing.
Notes
For most accurate results, I highly recommend using a digital kitchen scale if you have one.If you don't own a Bundt pan, use two 8 or 9-inch (20-23 cm) round cake tins.The cake batter will rise quite high in the Bundt pan but don’t worry! It will not overflow.Dab any collected pools of baking spray in the bottom of the cake tin with a paper towel before you add the cake batter.Use a handheld whisk if you don't own a hand mixer.I use clear vanilla extract for most light-coloured baking recipes to keep the colour light and pristine.