Preheat the oven to 180C/350F and line a 12 hole cupcake tray with liners.
Place the butter/margarine, sugar and lime zest into a large bowl or the bowl of your stand mixer and beat until light and fluffy. Around 2 minutes on medium-high speed.
Add in the eggs, scraping down the sides as necessary, and mix on medium speed until well incorporated and smooth.
Add in the flour, baking powder and salt (if using) and mix on low until the mixture begins to come together, then add the milk and continue to mix until you have a light, smooth batter with no lumps of flour.
Using a 2tbsp cookie scoop, divide the batter between the cupcake liners and then place in the oven for 18-22 minutes, until risen, lightly golden and an inserted skewer into the centre comes out clean.
Transfer to a wire rack to cool as soon as possible to stop liners peeling away from sides of cakes. Leave to cool completely.
Whilst the cupcakes are cooling, make the jam: place cherries, sugar and water into a medium sized saucepan over a medium heat. Bring to a boil, stirring frequently. Once boiling, turn down the heat to simmer for around 10 minutes until the cherries have cooked down and the mixture coats the back of a spoon. Leave to cool.
Once the cupcakes are cool, make the frosting: Place butter, icing sugar and lime zest into a large bowl, or the bowl of your stand mixer and beat for 2-3 minutes until light and fluffy. If required, add 1/2 - 1tbsp of milk. I used 1/2tbsp - you want a consistency that you can pipe through a nozzle, but will hold its shape.
Place the frosting into a piping bag fitted with an open star nozzle and then it's time to assemble!: Using a cupcake corer (I used the OXO Good Grips one) or a small knife, core each cupcake. If you're doing it with a knife, cut a circle 1 inch in diameter in the centre of each cupcake and remove the centre - make sure to leave a base of cake, I normally cut 3/4 of the way down.
Keep the cores and cut them into 1/8 inch thick tops so you can put them back over the jam when you've filled the cupcake. discard (or eat!) the leftover centres.
Spoon 1tsp of jam into the centre of each cored cupcakes and then top with your reserved tops.
Pipe a swirl onto each cupcake and garnish with a cherry and quarter slice of lime.
Cherry and Lime Cupcakes will keep in an airtight container, in the fridge, for 3 days.