Set a 1-quart saucepan over medium heat and add the sugar, water and lemon juice. Allow to heat, without stirring but swirling pot occasionally, until the sugar melts and turns amber in color, 5 to 7 minutes. Pour the caramel into a 10-inch cake pan and swirl the caramel to completely cover the base and about 1-inch up the sides. Allow to cool and harden.
In the bowl of an electric mixer, combine the remaining ingredients and beat, using a whip attachment, until well incorporated. Pour the mixture over the caramel into the prepared cake pan, set the cake pan inside a roasting pan and place in the oven. Add enough hot water to the roasting pan to come halfway up the sides of the cake pan and bake until the center of the flan is set, about 90 minutes. Remove from the oven, transfer to a cooling rack, and allow to cool at room temperature. Once cool, cover with plastic wrap and place in the refrigerator until thoroughly chilled, at least 4 hours and up to overnight.
Remove from the refrigerator after the flan has chilled and run a thin, sharp knife around the edge of the cake pan to help release the flan. Place a large plate or platter that is wide enough to fit comfortably over the rim of the cake pan and quickly but carefully invert the pan while holding the plate. The flan should fall onto the cake plate, with the excess caramel syrup pooled around the custard. Serve cold, or at room temperature.