Preheat the oven to 180°C (350°F) and line a muffin tin with 12 cupcake liners.

In a medium bowl, whisk together the flour, baking powder, bicarbonate of soda, and salt. Set aside.

In a large mixing bowl, whisk together the canola oil, sugar, crushed pineapple with juice, and vanilla extract until well combined.

Add the dry ingredients to the wet mixture. Mix until just combined, scraping down the sides of the bowl as needed. The batter will be quite thick.

Spoon the mixture evenly into the prepared cupcake liners, filling them about three-quarters full.

Bake for 20–25 minutes, or until the tops spring back when lightly touched. Allow the cupcakes to cool completely before frosting.

Make the pineapple buttercream: Using a hand mixer or a stand mixer fitted with the whisk attachment, beat the dairy free butter and vanilla extract for 1–2 minutes until creamy.

Add 3 cups of icing sugar and beat on medium speed until combined. Gradually add the pineapple juice, one tablespoon at a time. If the frosting is too soft, add up to 1 cup more icing sugar until the desired consistency is reached. Add a pinch of salt to taste.

Transfer the buttercream to a piping bag fitted with your preferred piping tip. Pipe swirls onto the cooled cupcakes. Garnish with pineapple chunks and maraschino cherries, if desired.