In a separate, smaller mixing bowl, whisk together the butter, yogurt, egg, vanilla and the juice of one of your bald lemons.
Combine the sugar and lemon zest in a medium mixing bowl. Use your fingers to rub the zest into sugar until the sugar is fragrant and pale yellow throughout. Whisk in the flour, poppy seeds, baking powder, baking soda and salt.
Preheat oven to 375 degrees Fahrenheit. Grease your muffin pan using butter or non-stick cooking spray. (Pro tip: grease only the bottoms and halfway up the cups so your muffin tops don’t flatten out while baking.)