Instructions

1. Heat the oven to 375ºF and prepare a muffin pan. Arrange a rack in the middle of the oven and heat to 375°F. Line a standard 12-well muffin pan with paper liners or coat the wells with cooking spray.
2. Melt the butter. Cut 1 stick unsalted butter into 4 pieces and place in a medium glass microwave-safe bowl. Microwave the butter in 4 to 6 (10-second) intervals, stirring between each. When the butter is mostly melted and only a few small pieces remain, stop microwaving and set aside at room temperature; the last few pieces will melt. (Alternatively, melt in a small saucepan on the stovetop over low heat, then pour into a medium bowl.)
3. Combine the sugar and lemon zest. Place 2/3 cup of the granulated sugar in a large bowl. Finely grate the zest of 2 medium lemons with a Microplane into the bowl (2 tablespoons zest). Rub the sugar and zest together with your fingertips until the sugar is moist and the mixture is fragrant, about 30 seconds.
4. Whisk the dry ingredients together. Measure 3 cups all-purpose flour using the spoon and sweep method and place in the bowl of lemon-scented sugar. Add 3 tablespoons poppy seeds, 1 tablespoon baking powder, 1/2 teaspoon baking soda, and 1/2 teaspoon kosher salt. Whisk to combine.
5. Whisk the wet ingredients together. Crack 2 large eggs into the bowl of melted butter. Juice the zested lemons into the bowl (6 tablespoons juice). Add 1 1/4 cups whole or low-fat plain yogurt (not Greek) and 1 teaspoon vanilla extract; whisk to combine.
6. Stir the wet ingredients into the dry. Pour the wet ingredients into the flour mixture and mix with a wooden spoon or rubber spatula until just combined and no dry flour remains; some lumps are fine. The batter will be quite thick, somewhere between a wet bread dough and a thick cake batter.
7. Divide the batter. Divide the batter among the prepared muffin wells, filling each one to dome over the top, about a heaped 1/3 cup of batter per well.
8. Top the muffins with sugar. Divide the remaining 6 teaspoons granulated sugar on top of the muffins, sprinkle each muffin with 1/2 teaspoon granulated sugar.
9. Bake and cool the muffins. Bake until the muffins are lightly golden and a toothpick or cake tester inserted into the center of a muffin comes out clean, about 20 minutes. Cool the muffins in the pan for 5 minutes, then transfer to a wire rack and cool at least 10 minutes more before serving.