Prepare the peach filling by adding all of the filling ingredients to a pot, except the cornstarch (cornflour).
Heat over a medium heat until the butter and sugar have melted.
Mix the cornstarch (cornflour) with 1 tsp water, mix to form a slurry.
Pour the cornflour slurry into the cooked peaches, stirring continuously to thicken the sauce. Remove from the heat and allow to cool.
Preheat the oven to 350 degrees F / 180 C. Line a 12 hole muffin tray with cupcake liners.
Next, prepare the cupcakes by sifting the flour, baking powder, cinnamon and salt into a mixing bowl.
Stir the lemon juice, milk and vanilla extract together in a small bowl and set aside.
Add the softened butter and brown sugar to the bowl of a stand mixer with the paddle attachment, and mix for 4 minutes or until light and fluffy.
Add the egg and mix.
Pour ½ of the dry ingredients into the butter mixture, mix on a medium speed to incorporate.
Next, add ½ of the wet ingredients and mix to combine. Add remaining dry and wet ingredients and mix for another 2-3 minutes until well combined.
Evenly divide the batter between the cupcake liners and bake for 15-20 minutes or until an inserted skewer comes out clean.
Remove and allow the cupcakes to cool for 5 minutes in the tray before transferring to a cooling rack to cool completely.
Prepare the buttercream by combining the softened butter and powdered sugar into the bowl of a stand mixer and beat on medium speed for 4-5 minutes.
Add the vanilla and cream and continue to mix for another 1-2 minutes.
To assemble the cupcakes, take a small knife and remove the center of each cupcake, making sure not to cut all the way to the bottom of the cupcake.
Fill the holes with the peach filling, reserving some of the filling.
Next, pipe or dollop buttercream on top of each cupcake and finish with the reserved peach filling.