Preheat the oven to 350 degrees F (175 degrees C). Line a 12-cup muffin tin with paper liners.

Stir flour, baking powder, baking soda, and salt together in a bowl.

Beat sugar and butter with an electric mixer in a large bowl until light and fluffy; the mixture should be noticeably lighter in color. Add 1 egg yolk and beat until fully blended into the butter mixture; repeat with the remaining egg yolk. Beat in almond extract and lemon zest.

Add flour mixture to the butter mixture in 2 batches, alternating with buttermilk, beating batter briefly after each addition. Fold in poppy seeds.

Beat egg whites in a glass or metal bowl until stiff peaks form. Fold egg whites into the batter. Spoon batter into the prepared muffin cups, filling each 2/3 full.

Bake in the preheated oven until muffins are golden and the tops spring back when lightly pressed, 15 to 18 minutes.

Remove muffins from the oven, turn out onto a wire rack, and cool.