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 smooth and well blended.
02 - Add flour, sugar, lemon zest, baking powder, and salt to the mug. Mix until just combined, scraping down the sides of the mug to ensure all dry ingredients are incorporated.
03 - Microwave on high power for 1 minute 30 seconds to 2 minutes, or until the cake has risen and the center is set.
04 - Let the cake cool for 2-3 minutes before serving. Enjoy directly from the mug, optionally garnished with powdered sugar, extra lemon zest, or a spoonful of yogurt.