Preheat oven to 375 degrees F (190 degrees C). Butter a jelly roll pan. Line it with buttered foil or buttered parchment paper.
Beat the eggs until thick and lemon colored. Gradually add 1 cup white sugar, beating constantly. Stir in water and vanilla extract. Fold in flour, baking powder, and salt. Pour batter into prepared pan.
Bake until cake is springy to the touch and beginning to shrink away from the sides of the pan, about 15 minutes.
Lay out a tea towel, and sprinkle it with confectioners' sugar. Turn the cake out on the towel. Peel off the paper or foil. Cut away crusty edges with kitchen shears or a sharp paring knife. Roll the cake up in the towel, and leave it to cool.
Whip the cream. Add unflavored gelatin and 1 tablespoon sugar. Fold in strawberries. Unroll the cake. Spread with the strawberry cream, and roll up again. Chill cake for at least 1 hour.
Before serving, dust cake with confectioners' sugar or top with additional whipped cream.