Preheat oven to 425 degrees F (220 C).
Grease 12 muffin cups.
In a bowl, sift together flour, baking powder, and salt.
In a separate bowl, cream together 1/2 cup sugar, eggs, butter, lemon zest, lemon juice, and milk.
Mix the creamed ingredients into the flour mixture until evenly moist.
Fold in the apples.
Spoon the prepared muffin cups.
Mix 1 tablespoon sugar and cinnamon, then sprinkle over the tops of the muffin batter.
Bake for 15 minutes in the preheated oven. Alternatively, insert a toothpick in the center of the muffin and see if it comes out clean.
Cool for 1-2 minutes before turning out onto wire racks to cool completely.
