Add sugar and water to a saucepan and stir together.
100 g sugar, 70 g water
Place saucepan over medium heat and bring to a simmer.
Let the mixture simmer for 3 minutes, then take it off the heat.
When the mixture cools to room temperature, stir in the lime juice and tequila.
60 g fresh lime juice, 30 g tequila
Store any unused syrup in the refrigerator. It will keep for several weeks.
Tequila Lime Buttercream
Add unflavored buttercream to a large bowl or the bowl of a stand mixer. Re-beat for about 2-3 minutes if it was previously refrigerated.
½ batch Easy Swiss Meringue Buttercream
Measure out the lime juice and, optionally, dissolve the True Lime powder into the juice.
30 g fresh lime juice, 1 packet True Lime
Add the juice to the buttercream and beat until it is fully incorporated.
Add the tequila to the buttercream and beat until it is fully incorporated.
30 g tequila
Using a clean spoon, taste the buttercream. You should be able to add about another tablespoon of liquid at this point if you need to adjust the flavor. Just add it and beat until incorporated.
Add food coloring if desired.
Combine the sugar and lime zest in a bowl by rubbing together with your fingers. Cover and let sit for about 30 minutes.
200 g sugar, 1 tablespoon lime zest
Preheat the oven to 325°F (165°C/gas mark 3).
Put cupcake liners into the cupcake baking tray.
Add sugar mixture, flour, baking powder, baking soda and salt to the bowl of a stand mixer fitted with the paddle attachment.
200 g sugar, 1 tablespoon lime zest, 155 g all purpose flour, 1 teaspoon baking powder, ¼ teaspoon baking soda, ¼ teaspoon fine grain salt
Mix on low speed until it is all combined.
Add the butter to the sugar/flour mixture and beat on medium low speed until the mixture looks all the same. It should be crumbly and sandy.
114 g butter
Add the eggs and mix on medium speed until fully incorporated.
Add the milk and mix until incorporated.
60 g whole milk
Add the lime juice and extract (optional) and mix until everything is well combined.
60 g lime juice, 1 teaspoon lime extract
Scrape down the sides of the mixer bowl and beat again on medium speed for about 20 seconds. This will give the cupcakes a bit more structure.
Portion the batter equally into the prepared cupcake liners. You can do this with an ice cream scoop, a spoon or a piping bag. Just fill them to about halfway full for flat topped cupcakes, or ⅔ full for larger cupcakes. You'll need to bake them a minute or two longer for the larger cupcakes.
Bake the cupcakes for 17-19 minutes. The cupcakes will be done when they spring back when touched with your finger. They should be 205°F (96°C) internally when checked with a probe thermometer.
Let the cupcakes cool for 10 minutes in the pan and then transfer them to a cooling rack.
Using a toothpick or skewer, poke holes in the top of each cupcake. Use a pastry brush or spoon to top each cupcake with the Tequila Lime Simple Syrup.
Frost each cupcake with the Tequila Lime Buttercream. You can use an offset spatula or a piping bag.
Sprinkle coarse-grained sugar and/or salt on top of the buttercream if you like. Then add a small wedge of lime to top each cupcake.
coarse-grained sugar and/or salt, 1 lime
These cupcakes will keep at room temperature for about 2 days. If you would like to store them longer, I recommend wrapping each cupcake individually and freezing them in an airtight container.