Preheat oven to 170 fan and line a 12-hole cupcake tin with paper cases.
Cut a piece out of each pineapple ring so they fit into paper cases.
Beat butter and sugar together until light and fluffy, then add eggs, flour, bicarb, and vanilla and mix well. Add enough milk to loosen mixture a little.
Fill each paper case 3/4 full, then top with pineapple ring. Scatter a little Demerara sugar onto each cupcake and bake for 20-25 minutes or until skewer comes out clean.
Place jam into piping bag and snip the end. Once cupcakes are cooled, poke a little hole into each cupcake with a skewer and pipe in the cherry jam.
To make the buttercream, beat butter then add icing sugar until smooth and light. Add coconut extract and enough milk to loosen.
Place buttercream into piping bag with a round nozzle and pipe a swirl on top. Roll cupcake into toasted coconut, then add a swirl to the top of each one.
Place cherries into glitter pot and shake to remove the excess. Top each cupcake with a cherry!