Begin by preheating your oven to 350°F and lining an 8-inch cake tin with non-stick baking parchment paper.
In a separate saucepan, bring 4 tablespoons of water to a boil, then melt 1 tablespoon of butter into the hot water and set aside. In a large mixing bowl, beat 3 eggs together with 1 cup of sugar until the mixture becomes very thick and pale—this indispensable step typically takes at least 10 minutes of beating and is essential for incorporating air into your batter.
Sift 1 cup of self-raising flour to remove any lumps, then gently fold it into the egg-sugar mixture using a spatula or folding technique to maintain the airiness you've created. Carefully fold in the butter-water mixture last, being gentle to preserve the light texture.
Pour the prepared batter into your lined cake tin and bake for approximately 25 minutes, until the cake is springy to the touch and a light golden color.
Once baked, remove the cake from the oven and allow it to cool completely on a wire rack before proceeding. This cooling step is important as it allows the structure to set properly before you slice and fill the cake.
Once cooled, slice the cake horizontally into two layers. Fill the center with whipped cream and fresh strawberries, then reassemble the cake. The result is a light, fluffy sponge cake with a delicious fruit and cream filling that's perfect for any occasion.