Prep: Preheat oven to 350°F (177°C). Line 18–20 muffin cups with paper liners.
Dry ingredients: In a medium bowl, whisk together flour, baking powder, and salt. Set aside.
Wet ingredients: In a large bowl, whisk together ¾ cup cooled brown butter, granulated sugar, eggs, vanilla, and Greek yogurt until smooth.
Combine: Add half the dry ingredients to the wet mixture and mix until just combined. Pour in half the milk, mix gently, then add the remaining dry ingredients followed by the remaining milk. Mix only until the batter is smooth—do not overmix.
Bake: Divide batter evenly among cupcake liners, filling each about ⅔ full. Bake 22 minutes, or until a toothpick inserted in the center comes out clean. Cool completely on a wire rack.