Lemon Strawberry Layer Cake

STEP 1: BAKE THE LEMON SPONGE
Preheat the oven to 350°F (175°C) and line a Swiss roll tin (about 12×17 in / 30×43 cm) with parchment. Whisk the eggs and granulated sugar in a heatproof bowl over a pan of simmering water until just warm, then whip on high for 5–7 minutes to the ribbon stage — thick, pale, and tripled in volume. Sift in the flour and salt and fold in over two additions, then fold in the lemon zest and juice. Drizzle the cooled melted butter down the side of the bowl and fold in gently. Spread evenly in the tin and bake 12–15 minutes until springy to the touch. Turn out, peel away the parchment, and cool completely.

STEP 2: MAKE THE STRAWBERRY REDUCTION
Combine the strawberries, granulated sugar, and lemon juice in a saucepan. Cook over medium heat, mashing, for 12–15 minutes until thick, jammy, and reduced by roughly half. Pass through a fine-mesh sieve for a smooth, intense purée and cool completely. This single reduction flavours both the filling and the buttercream, so the fruit reads clearly throughout.

STEP 3: WHIP THE STRAWBERRY MASCARPONE CREAM
In a cold bowl, whip the heavy cream to soft peaks. In a second bowl, loosen the mascarpone with the sifted powdered sugar and 1/3 cup cooled strawberry reduction, then fold in the whipped cream until just combined and stable. Do not overwhip, as mascarpone can split. Chill until needed.

STEP 4: MAKE THE STRAWBERRY SWISS MERINGUE BUTTERCREAM
Whisk the egg whites and granulated sugar in a heatproof bowl set over simmering water. Heat, whisking constantly, to 160°F (71°C); rub a little between two fingers — it must feel completely smooth, with no sugar grains. If you still feel grit, keep heating until it dissolves. Whip on high to a stiff, glossy meringue that has cooled to room temperature (the bowl should feel neutral, not warm). With the paddle on medium, add the softened butter a cube at a time; it may look curdled — keep beating and it will come together silky and smooth. Beat in the salt and 1/4 cup cooled strawberry reduction.

STEP 5: BUILD THE CAKE VERTICALLY
Trim the cooled sponge to a clean rectangle and cut it lengthwise into four even strips 3 in (7.5 cm) wide — four strips use the full width of the sheet with no offcut wasted. Brush each strip lightly with the lemon syrup, then spread a thin, even layer of the mascarpone cream right to the edges. Roll the first strip into a tight pinwheel and stand it on its cut edge on the cake board. Wrap the next strip around the core, keeping the bottom edge flush with the board and the tension even; continue with the remaining strips to build one even cylinder about 3 in (7.5 cm) tall. Chill at least 30 minutes until firm.

STEP 6: CRUMB COAT AND SMOOTH JACKET
Apply a thin crumb coat of the strawberry buttercream and chill 20 minutes. Apply a second, generous coat and smooth the sides with a bench scraper held vertical against the turning cake for a clean, even pink jacket. Chill again to set.

STEP 7: MAKE THE CARAMEL SHARDS
Heat the granulated sugar and water in a light-coloured pan over medium heat without stirring until a deep amber caramel forms. Pour a thin layer onto a silicone mat or oiled parchment and leave to set hard, then snap into shards. Choose just three to five of the cleanest shards.

STEP 8: CHILL AND SERVE
Chill the finished cake until ready to serve. Just before serving, stand the caramel shards in a small off-centre cluster on top — an accent, not a crown. Slice with a warm, dry knife to reveal the clean vertical spiral of lemon sponge and strawberry cream.