In a medium saucepan, combine water and unsalted butter over medium heat. Stir until the butter melts completely. Once boiling, remove from heat and stir in all-purpose flour and salt. Mix vigorously until the dough pulls away from the sides of the pan. Let it cool for a few minutes.

Beat the eggs in a separate bowl. Gradually add them into the cooled dough, one at a time, mixing well after each addition until you have a smooth and glossy batter.

Preheat your oven to 400°F (200°C). Line two baking sheets with parchment paper. Using a piping bag, pipe long lines of dough onto the prepared sheets. Bake for about 20-25 minutes or until golden brown.

In a small saucepan, whisk together lemon juice, lemon zest, sugar, and cornstarch over medium heat until it thickens. In another bowl, combine milk with egg yolks and whisk well. Slowly pour this mixture into the saucepan while stirring. Cook for an additional minute before removing from heat and adding vanilla extract. Let cool completely.

In a mixing bowl, beat heavy cream until soft peaks form. Gently fold in the cooled lemon mixture until fully combined.

Once the eclairs have cooled, make small slits at one end of each éclair. Fill your piping bag with the lemon cream mixture and carefully fill each éclair.

Top each filled éclair with fresh raspberries. Mix together powdered sugar and lemon juice to drizzle over them if desired.