Preheat your oven to 350°F (175°C).
Grease your muffin tin with butter or line it with muffin liners.
In a large mixing bowl, whisk together the all-purpose flour, rice flour, baking powder, lemon zest, and kosher salt.
In a separate bowl, cream together the room-temperature unsalted butter and granulated sugar until light and fluffy.
Add the eggs one at a time to the butter-sugar mixture, mixing well after each addition.
Gradually add the dry ingredient mixture to the wet ingredients, alternating with the whole milk. Mix until just combined.
Spoon the batter into the prepared muffin tin, filling each cup about ¾ full.
Sprinkle a little granulated sugar on top of each muffin batter.
Place the muffin tin in the preheated oven and bake for 20-25 minutes.
Once baked, let the muffins cool in the pan for about 5 minutes before transferring them to a wire rack.