Line a 25 × 40 cm baking tray with lightly greased parchment paper. Preheat the oven to 180°C (350°F).

Combine the flour and baking powder, then sift to ensure a fine, lump-free texture.

Beat the eggs, sugar, and vanilla until the mixture becomes pale, thick, and triples in volume.

Mix in the vinegar briefly to lighten and clean up the flavour.

Add the flour mixture one spoonful at a time, folding carefully with a spatula to preserve the airy texture.

Pour the batter into the tray and smooth the surface. Bake for 10–12 minutes, or until lightly golden and springy to the touch.

Turn the sponge out onto a clean towel, remove the parchment, and roll it immediately with the towel. This prevents cracking and helps the sponge keep its shape.

Unroll gently, trim the edges, spread the jam, and roll again. Wrap in foil and refrigerate 30 minutes to set.

Remove the foil, trim the ends neatly, and dust with icing sugar or frost with chocolate or buttercream.