Preheat oven to 200°C
In a large mixing bowl whisk together flour+baking powder+baking soda+salt for 30 seconds.
In the bowl of your stand mixer fitted with the paddle attachment start by beating together lemon zest and sugar to really disperse all the lemon zest evenly.
Next, add in room temperature butter + 1 tbsp of your vegetable oil. Beat until fluffy, and lighter in color (about 5 min). Scrape down your bowl with a spatula.
Continue mixing in the rest of your canola oil and mix until incorporated.
Add in each egg one at a time, making sure the egg is well combined before adding the next one. Scrape your bowl.
Add in your egg yolk + vanilla and give it one last mix. Set aside
In a bowl with a spout (for easy pouring) add your milk + sour cream + 3tbsp lemon juice). Give it a whisk. Set aside.
Add ½ of your egg mixture and ½ of your milk mixture into your flour. Using a spatula start folding it in. Then proceed to add the second ½ of your egg and the second ½ of your milk mixture into your flour. Fold well. The mixture should be thick. If you used a thicker sour cream you might need to thin out the mixture with 1-2 tbsp of milk. Set aside.