Pre-heat oven to 325F (conventional) and prepare a 8.5x4" loaf pan with butter and parchment paper

Add the sugar and lemon zest to a bowl, and rub them together for 1-2 minutes until the mixture starts to look fluffy

Add the eggs, vanilla and lemon extract and whisk using an electric hand mixer or stand mixer for 3-4 minutes until the mixture is very light in color and thick and ribbony in consistency

Add the butter, oil and milk to a saucepan and heat on medium heat until the butter melts and the mixture starts to simmer

Pour the hot butter mixture into the egg and sugar mixture slowly while continuing to whisk

Sift the flour, cornstarch, baking powder, baking soda and salt into the batter, and gently fold using a hand whisk or rubber spatula until combined

Lastly, add the sour cream and lemon juice and gently fold until combined. Avoid overmixing

Pour the batter into the prepared loaf pan

Optional: Add the softened butter to a piping bag or ziploc bag. Snip a small hole and pipe a thin line down the middle of the loaf pan. This will help control the crack as the cake rises

Bake for 45-55 minutes, checking at the 45 minute mark with a toothpick. It should come out with moist crumbs attached (not wet batter). Timing will vary depending on your oven and pan

Let the cake cool down for 20 minutes

In the meanwhile, prepare the icing by mixing together the ingredients

Once the cake has cooled, remove it from the pan carefully. Spread on the lemon icing, and garnish with some more lemon zest

Slice in and enjoy!