• 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.

Cinnamon Streusel

• In a small bowl add flour + brown sugar + pinch of salt + cinnamon mix well.
• Add in your cold pieces of butter. Using your finger, pinch together the butter with the flour mixture until a crumble is formed. Set aside.

Baking

• Grease your muffin tin with some cooking spray or vegetable oil.
• Add about 1 tablespoon of your batter to each cavity. Sprinkle in about 1-1.5 teaspoons of your cinnamon streusel. Then cover with more of your batter making sure to reach the top of the cavity. Use a metal offset spatula to smooth and spread down the tops.
• Place in your oven and bake for 15-18 minutes until a toothpick inserted into the center of the muffins comes out clean.
• Remove muffin tin from oven and place on a cooling rack. Allow muffins to cool in the tin for 10 min. Then invert and allow them to continue to cool on a cooling rack.

Lemon Glaze

• While your muffins are baking make the glaze. Add powdered sugar and lemon juice and whisk until fully incorporated. If you want a thicker glaze that holds its shape better add 1-2 tbsp more of powdered sugar.
• While muffins are sightly warm drizzle with glaze or dip the muffin top into the glaze.
• Store in an airtight container at room temperature for 2-3 days.