Grease 11-inch (28 cm) flan pan with raised centre. Line raised centre with circle of parchment paper; grease and dust with flour. Set aside.
In small bowl, sift together flour, baking powder and salt; set aside.
In medium bowl, using an electric mixer, on medium-high speed, beat eggs and sugar until pale yellow, thick and batter falls in ribbon-like fashion when beaters are lifted, about 10 minutes. Stir in water, lemon juice and vanilla. Gently stir in flour mixture a third at a time. Spread in prepared pan evenly to edge.
Bake in 350F (180C) oven for 20 to 25 minutes or until golden and top springs back when touched. Let cool in pan on wire rack for 5 minutes. Loosen edge and invert onto wire rack; remove parchment paper. Let cool completely.