Preheat your oven to 350°F (175°C). Grease a 9-inch round cake pan with butter or non-stick baking spray.
Step 1
Whisk together the flour, baking soda, and salt in a medium bowl.
Step 2
In a large bowl, cream the softened butter using a mixer until smooth. Add both sugars and continue to beat on medium speed until the mixture is smooth and well combined, about 2 minutes.
STEP 3
Mix in the egg and vanilla extract until fully incorporated. Scrape down the sides of the bowl as necessary.
STEP 4