01 - In a microwave-safe mug (at least 12 oz capacity), whisk together cottage cheese, egg, milk, melted butter, lemon juice, and vanilla extract until completely smooth and incorporated.
02 - Add flour, sugar, lemon zest, baking powder, and salt to the mug. Mix until just combined, ensuring no dry pockets remain, scraping down the sides of the mug as needed.
03 - Microwave on high power for 1 minute 30 seconds to 2 minutes, until the cake has risen and the center is fully 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 a spoonful of yogurt.