Preheat oven to 350 degrees F (175 degrees C). Grease 12 muffin cups, or line with paper muffin liners.
Stir flour, poppy seeds, baking powder, and baking soda together in a bowl.
Cream the sugar and butter together in a large bowl. Add the whole egg, then the egg yolk, allowing each to blend into the butter mixture before adding the next.
Stir sour cream, vanilla, lemon peel, and lemon extract into the sugar mixture until well combined. Add flour mixture to sour cream mixture and stir until just moistened. Spoon batter into prepared muffin cups, filling each cup about 3/4 full.
Bake in the preheated oven until golden and the tops spring back when lightly pressed, about 15 minutes. Cool for 5 minutes before removing to wire racks.
