Preheat oven to 375° F / 190° C. Line a half sheet rimmed baking tray with parchment and set aside until ready to use.

In a large bowl, sieve flour, baking powder, baking soda, and salt.

In a separate mixing bowl or the bowl of a stand mixer, mix the butter on high speed until light and fluffy.

Add the sugar, followed by egg, vanilla extract, and lime zest, mixing on high speed until well combined.

Add the dry ingredient mixture to the batter, followed by milk. Mix on low speed until just combined.

Mix in pink gel food coloring, if using.

Transfer batter to a piping bag fitted with a 1/2-inch round tip.

Pipe 2-inch rounds onto prepared trays, allowing space for the cakes to spread.

With damp fingertips, pat the top of each cake to create a smooth, evenly domed surface.

Bake in preheated oven for 11-12 minutes, or until edges of cakes are very lightly golden brown and cakes spring back lightly when touched. Cool on tray.

While cakes are cooling, prepare the jam and the buttercream.

Raspberry-Mint Jam:

Add the raspberries and sugar to a small saucepan.

Cook over medium heat, stirring occasionally, for 5 minutes or until berries break down.

Remove from heat. Allow to cool briefly, then pass through a fine mesh strainer to remove the seeds.

Stir in the lime juice and the chopped mint.

Refrigerate until ready to use.

Lime Buttercream:

In a large mixing bowl or the bowl of a stand mixer, mix the softened butter on high speed until light and fluffy.

Gradually add the confectioner’s sugar, alternating with the milk and mixing well after each addition.

Add the lime juice, lime zest, sea salt, and gel food coloring (if using) and mix until smooth and creamy, about 3-5 minutes. If necessary, add more confectioner’s sugar or milk to adjust the consistency. The buttercream should be smooth and creamy, but thick and stiff enough that it won’t lose its shape when piped. (If your buttercream is too thin, the fresh raspberries will slide out of place!)

Transfer to a piping bag fitted with a 1/2-inch star or other decorative piping tip.

Assembly:

Transfer raspberry jam to a piping bag.

Divide the cakes into pairs, choosing tops and bottoms that are as close as possible in size.

Pipe a generous ring of lime buttercream on the flat side of the ‘bottom’ cakes.

Pipe raspberry jam in the middle of each ring.

Add 4-5 fresh raspberries around the outer edge of the buttercream.

Top each with the second cake to create a sandwich.