01 - In a microwave-safe mug with at least 12 oz capacity, whisk together cottage cheese, egg, milk, melted butter, lemon juice, and vanilla extract until completely smooth.
02 - Add flour, sugar, lemon zest, baking powder, and salt to the mug. Mix until just combined, ensuring to scrape down the sides and incorporate any dry pockets.
03 - Microwave on high power for 1 minute 30 seconds to 2 minutes, watching until the cake has risen and the center appears set.
04 - Allow the cake to cool for 2-3 minutes before serving. Enjoy directly from the mug, optionally dusted with powdered sugar, extra lemon zest, or topped with yogurt.