Design Eat Repeat

0 For best success, be sure to read the tips & tricks in the blog post above! I recommend mixing this by hand with a spatula, not an electric mixer.
1 In a medium-sized mixing bowl, mix together softened unsalted butter ([adjustable]½ cup, i.e. 1 stick), granulated sugar (1 cup), lemon extract (1 tablespoon), and fresh lemon zest (½ tablespoon[/adjustable], optional) until smooth and no more butter chunks remain. This will infuse the butter and sugar with the lemon flavor.If your butter isn't incorporating easily, it's too cold. You can pop the bowl in the microwave in 5-second increments until it's easy to stir.
2 Add vanilla extract ([adjustable]2 teaspoons), eggs (2 large), baking powder (1 teaspoon), and salt (½ teaspoon[/adjustable]), then mix until incorporated.
3 Add all-purpose flour ([adjustable]1 ¼ cups) and cornstarch (2 tablespoons[/adjustable]), then mix until just combined. Lastly, add milk ([adjustable]¼ cup) and vegetable oil (¼ cup[/adjustable]) and stir until combined.
4 Grease an 8×4″ light-metal loaf pan and line with parchment paper. Pour batter into pan, then gently tap against the counter to release any air bubbles.
5 Read these baking instructions carefully! Bake at 350°F for 60 minutes total, but when there are 15 minutes left, tent a piece of foil on top to prevent the top from overbrowning. This will allow the inside to finish baking without overbaking the top.* Because ovens bake differently, use a toothpick or skewer to check for doneness around 45 minutes. If you're using a dark metal pan, you will want to check for brownness earlier around the 30 minute mark. You will also likely not need to bake for the full 60 minutes.
6 Allow the loaf to FULLY cool before adding glaze.
Glaze: 
8 In a small bowl, mix together softened unsalted butter ([adjustable]1 tablespoon), powdered sugar (1 cup), salt (⅛ teaspoon), fresh lemon juice (1 tablespoon), and milk or heavy cream (1 tablespoon[/adjustable]). If your glaze is too thick to pour, add a bit more milk. 
9 Stir until smooth, then pour over the cooled loaf. To prevent it from pooling on the sides, I sometimes like to pour half on at once, allow it to set, then add the second half.
10 After allowing the glaze to fully set, cut into thick slices and enjoy!