Heat your oven to 375°F. While it preheats, line a 9x13 inch baking sheet (or similar rectangular pan) with parchment paper, then lightly butter the paper. This prevents sticking and makes it easier to flip the delicate cake later. Set aside.

While the oven heats, sift together the flour and 1 1/2 tablespoon icing sugar in a small bowl to remove any lumps and aerate the flour—this ensures a light, tender crumb. Set aside. In a separate bowl, whisk together the rhubarb compote, 3/4 cup sifted icing sugar, lemon juice, 1 teaspoon vanilla essence, and lemon zest until well combined. I like to taste this filling at this point and adjust the lemon juice if needed—it should have a bright, tart edge that balances the sweetness of the cake.

Using an electric mixer on high speed, beat the room-temperature eggs with 3/4 cup sugar and 1 1/2 teaspoon vanilla essence for about 10 minutes until the mixture is pale, thick, and roughly tripled in volume. The mixture should form a ribbon when the beaters are lifted—this incorporates air that gives the cake its characteristic light, spongy texture. I always make sure my eggs are at room temperature because cold eggs take longer to whip and won't incorporate as much air.

Gently sift the dry ingredient mixture from Step 2 over the whipped egg foam in two additions, folding carefully with a rubber spatula after each addition until just combined—do not overmix or you'll deflate the air bubbles. Pour the batter evenly onto the prepared pan and bake for about 10 minutes until the top is light golden and springs back when lightly touched. The cake should still be moist and tender, not dry.

Remove the hot cake from the oven and immediately turn it out onto a clean piece of parchment paper. Gently peel away the baking paper from the top of the cake. While the cake is still warm, spread the rhubarb mixture from Step 2 evenly across the surface, leaving a small border on all sides. Starting from one long edge, tightly roll the cake into a log using the parchment paper to help guide it, then carefully slide it onto a serving platter seam-side down.

Whisk together 3/4 cup sifted icing sugar and 1 tablespoon fresh lemon juice until smooth and pourable—the glaze should be thick enough to coat the back of a spoon but thin enough to drizzle. Drizzle the glaze over the cooled rhubarb jelly roll in a decorative pattern. Let it set for a few minutes before serving.