Step 1

Preheat oven to 180 °C (350°F) conventional (see note 2 if using a convection oven with a fan) and grease a square 8x8 inch cake tin (I use my homemade cake release). Once greased, line with a piece of parchment paper that is long enough so there is some overhang on two opposite edges of the tin. This will make it easier to pull the brownies out once done.

Step 2

Sift together flour, cornstarch and salt. Using a whisk or fork, mix until well combined and set aside for now.

Step 3

In a large mixing bowl add in white sugar and fresh lemon zest. Using your fingers, rub the lemon zest into the sugar until the sugar has a light yellow tinge to it (about 30 seconds).

Step 4

Add in warm melted butter, unflavored vegetable oil, eggs, lemon juice and vanilla. Using a whisk, mix until combined and smooth, but avoid overmixing (you don't want to incorporate too many air bubbles into the batter).

Step 5

Add in the dry ingredients from earlier and using a spatula, gently fold until just combined. Do not overmix.

Step 6

Pour the batter into the prepared cake pan (the batter should be thin). Give the tin a little shake to evenly distribute the batter and then drop it lightly on the counter twice. Bake for 22 minutes, or until a toothpick comes out almost clean (you want to have a very small amount of uncooked batter or moist crumbs on the toothpick - this will ensure the brownies don't overbake).

Step 7

Allow to completely cool in the cake tin (1-2 hours).

Step 8

Once cooled, run a thin knife (or spatula) around the edges of the pan that have no parchment paper and then carefully use the excess parchment paper hanging over the edges to carefully lift the brownie out of the cake pan.

Step 9

Prepare the lemon glaze by combining the powdered sugar and lemon juice. Mix with a spoon until combined and smooth. You want the glaze to be thick, but spreadable (see note 3).

Step 10

Spread the glaze evenly over the top of the brownie. Allow it to set for 30 mins to an hour (you should be able to touch the top without any of the frosting sticking to your finger) and then slice and serve!