Preheat your oven to 350°F (180°C). Lightly butter a 6-cup muffin tin or silicone mold to prevent sticking.

In a small saucepan over medium heat, combine the sugar and water. Let it cook without stirring until it turns a rich amber color, then pour it into the bottoms of the muffin cups.

Place half a pineapple slice in each muffin cup on top of the caramel, gently pressing them down.

In a mixing bowl, whisk the eggs and sugar until pale and slightly thickened. Add the mascarpone and vanilla extract, mixing until smooth. Sift in the flour and baking powder, then gently fold until just combined.

Spoon the batter evenly over the pineapple slices in each cup, filling about 3/4 of the way full. Bake for 20–25 minutes, or until a toothpick comes out clean.

Allow the cakes to cool in the tin for about 10 minutes, then carefully flip them onto a serving plate while still warm.