The night before, get your eggs and butter out of the fridge. See notes.
Preheat the oven to 200C/400F. Grease and line your loaf pan.
Weigh out the sugar in small bowl and set aside.
Weigh out the flour and whisk it together with the baking powder and salt. Sieve once and set aside.
Place the room temperature butter in your stand mixer with the paddle attachment. Beat on a low-medium speed until it is soft and pliable, scraping down the bowl as necessary. Depending on the temperature of your butter, this might only take a minute or two.
Once the butter is soft and pliable, add the oil and sugar. Scrape down the sides and turn the mixer to a medium-high speed (I use speed 5 or 6 on my KitchenAid). Beat for 3-5 minutes until the mixture is super light in colour and fluffy in texture. This may take longer in winter, so be patient (but don’t leave it for too long or you’ll deflate the mixture).
Once the butter and sugar are creamed, turn the mixer to a low speed and beat in one egg at a time. I find I need to scrape the sides down after each egg.
After the 3rd and 4th eggs, the batter will look a little lumpy and split. This is normal – gluten free baking requires more moisture than regular baking. Continue scraping the sides down and beating on low until the eggs are combined (even if it looks lumpy).
Add the vanilla bean paste while the mixer is off (it gets tangled in the paddle) and mix just to combine.
Add the flour mixture in 3 lots while the mixer is running on low. In between adding the flour, add the tablespoon of room temperature milk.
Continue adding flour and mixing until just combined until you have incorporated all the flour. Scrape down the sides to ensure there’s no butter heavy bits, and gently mix one last time.
Use a spatula to gently transfer the mixture to the lined and greased loaf tin. Gently spread the mixture into all corners of the tin and create an even top.
Place the tin in the oven and turn the heat down to 160C/320F. Bake for 1 hour 10 minutes or until a skewer comes out clean.