Warm the lemon juice, 1 1/2 cups (360 ml) water, and the sugar to boiling. Stir until the sugar is completely dissolved.
Pour the water into a small mixing bowl and sprinkle the gelatin over its surface. Let the gelatin soften for 5 minutes.
Add the gelatin paste to the lemonade and stir until fully dissolved.
Preheat a fan-forced oven to 160C (320F) or 180C (356F) for a conventional oven. Line a cupcake tin with cupcake liners.
In the bowl of a stand mixer fitted with the paddle attachment, add the flour, baking powder, caster sugar and salt. Turn mixer on low speed and allow it to mix for a couple minutes to help everything combine well (alternatively you may do this by sifting the ingredients together). Add the softened butter and let it mix until it resembles a fine sand like texture.
Next, add milk, eggs, yogurt, oil and vanilla extract in a large jug and whisk well.
Add wet ingredients to dry ingredients in a slow and steady stream until no dry ingredients are visible. Scrape down the bowl add lemon zest and yellow food dye and mix for another 20 seconds.
Fill each cupcake liner 3/4 of the way (using an ice cream scoop to transfer the batter into the cupcake liners makes this a quick and easy process otherwise you can use two tablespoons). Bake for 20-25 min or until a toothpick inserted comes out clean. Allow them to cool completely on a wire cooling rack before frosting.
While your cupcakes are baking, and cooling prepare your buttercream frosting by adding lemon essence or zest and yellow food dye. Mix until well combined.
Fit the end of a piping bag with a Wilton 6B tip and frost your cupcakes in a donut swirl as demonstrated in the video.
Top with lemonade jelly and a yellow striped straw if you’re feeling fancy!
Cupcakes can be stored in an airtight container for up to three days.