Step 1: Prepare the Baking Equipment

Preheat your oven to 350°F (175°C). Line a jelly roll pan (approximately 10×15 inches) with parchment paper, ensuring it extends slightly over the edges for easy removal.

Step 2: Make the Sponge Batter

1. In a large mixing bowl, beat the eggs and granulated sugar using an electric mixer on high speed for about 5 minutes. The mixture should turn pale and thick, forming ribbons when lifted. This step is crucial for achieving a light sponge.
2. In a separate bowl, sift together the flour, baking powder, and salt. Gently fold the dry ingredients into the egg mixture using a spatula. Be careful not to deflate the batter.
3. Add the lemon zest and fold gently until incorporated.

Step 3: Bake the Sponge Cake

1. Pour the batter into the prepared pan, spreading it evenly with a spatula.
2. Sprinkle the blueberries evenly over the top.
3. Bake in the preheated oven for 12-15 minutes, or until the cake is golden and springs back when lightly touched.

Step 4: Roll the Cake

1. While the cake is baking, prepare a clean kitchen towel by dusting it with confectioners’ sugar.
2. Once baked, immediately turn the cake onto the prepared towel. Carefully peel off the parchment paper.
3. Starting from one short end, roll the cake and towel together while it is still warm. This helps the cake hold its shape without cracking later. Let it cool on a wire rack.

Step 5: Prepare the Filling

1. In a chilled mixing bowl, whip the heavy cream, confectioners’ sugar, and vanilla extract until stiff peaks form.
2. Unroll the cooled cake and brush the surface with lemon juice for extra moisture and flavor.
3. Spread the whipped cream filling evenly over the cake, leaving a ½-inch border around the edges.

Step 6: Re-Roll and Chill

1. Carefully roll the cake back up, this time without the towel. Use gentle pressure to keep it tight but not too firm.
2. Wrap the rolled cake in plastic wrap and chill for at least 30 minutes to allow the flavors to meld and the cake to set.