Here are the steps to create these delightful lemon filled cupcakes:

1. Preheat the Oven: Set your oven to 350°F (175°C) and line a cupcake tin with paper liners.

2. Mix Dry Ingredients: In a medium bowl, sift together flour, baking powder, and salt. Set aside.

3. Cream Butter and Sugar: In a large mixing bowl, beat the softened butter and granulated sugar until light and fluffy.

4. Add Eggs & Flavor: Add the eggs one at a time, mixing well after each addition. Stir in vanilla extract and lemon zest.

5. Combine Mixtures: Gradually add the dry ingredients to the butter mixture, alternating with milk. Mix until smooth and well combined.

6. Fill Cupcake Liners: Spoon the batter into the prepared cupcake liners, filling each about 2/3 full.

7. Bake: Place the cupcakes in the preheated oven and bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean.

8. Cool the Cupcakes: Once baked, remove the cupcakes from the oven and let them cool in the pan for about 10 minutes. Then, transfer them to a wire rack to cool completely.

9. Prepare the Lemon Filling: In a small bowl, combine powdered sugar, lemon juice, and lemon zest until smooth.

10. Fill the Cupcakes: Once cooled, use a small knife or a cupcake corer to remove the center of each cupcake. Fill each cavity with the lemon filling.

11. Make the Frosting: In a mixing bowl, beat the softened butter until creamy. Gradually add powdered sugar, heavy cream, and vanilla extract. Beat until fluffy.

12. Frost the Cupcakes: Frost the cooled and filled cupcakes generously with lemon frosting.

13. Garnish: Optionally, top each cupcake with additional lemon zest or a small slice of lemon for added flair.