Preheat the oven to gas mark 5, 190°C (fan 170°C), and line two muffin tins with cupcake liners. In a mixing bowl, beat the butter and caster sugar with an electric whisk for 4 to 5 minutes until the mixture is pale and well combined.

In a separate bowl, sift together the flour, bicarbonate of soda, salt, and matcha powder. Add the dry ingredients to the butter and sugar mixture, mixing on low to medium speed until just combined.

In a jug, whisk together the vegetable oil, buttermilk, eggs, vanilla extract, apple cider vinegar, and a few drops of green gel food coloring if using. Gradually pour the wet ingredients into the mixing bowl and stir until just combined.

Divide the batter evenly among the cupcake cases and bake for 20 to 22 minutes, or until the cupcakes have risen and a cocktail stick inserted in the center comes out clean.

Transfer the cupcakes to a wire rack to cool completely; note that they will level out as they cool.

For the buttercream, combine the chopped strawberries, caster sugar, lemon juice, and vanilla extract in a pan and bring to a boil. Reduce the heat and simmer gently for 15 minutes, stirring occasionally, until the mixture has reduced by half. Remove from the heat and allow it to cool completely. In a separate bowl, beat the softened butter with an electric whisk for 5 minutes until pale and fluffy.

Gradually add the icing sugar, mixing on low speed until combined, then increase to high speed and beat for 4 to 5 minutes until light and fluffy. Add pink gel food coloring if desired, along with 3 tablespoons of the cooled strawberry reduction, and beat on high speed until fully incorporated.

If the buttercream is too stiff to pipe, add an additional tablespoon of strawberry sauce and a little hot water, one teaspoon at a time, until the desired consistency is reached.

Transfer the buttercream to a piping bag fitted with a large star tip and pipe onto the cooled cupcakes.

Top each cupcake with a strawberry half and dust lightly with the remaining 2 teaspoons of matcha powder. Store the cupcakes in an airtight container in the refrigerator for up to five days.