Preheat the oven to 375℉. Line a 15x10x1-inch pan with parchment paper; generously grease the foil or paper with shortening. Then sprinkle it lightly with powdered sugar.
In a medium bowl, use an electric mixer to beat the eggs on high speed for about 5 minutes, or until very thick and pale lemon-colored. Gradually beat in the granulated sugar. Beat in the water and vanilla on low speed. Gradually add the flour, baking powder and salt, beating on low speed just until smooth. Pour the batter into the pan, spreading evenly to the corners.
Bake for 12 to 15 minutes or until a toothpick inserted into the center comes out clean. Immediately loosen the cake from the sides of the pan and turn upside down onto a slightly damp towel that has been generously sprinkled with powdered sugar. Carefully peel off the parchment paper. Trim off any unruly edges of the cake if necessary. While the cake is hot, carefully roll the cake and towel from the narrow end. Cool on a cooling rack for at least 30 minutes.
Unroll the cake. Beat the lemon curd slightly with a fork to loosen it up; spread the lemon curd over the cake. Roll up the cake again, without the towel; place the cake seam-side-down on a serving plate. Sprinkle with powdered sugar.