Start by placing the flour, salt, and sugar in a large bowl. Mix these dry ingredients together with a fork, ensuring there are no lumps.
In a separate bowl, whisk the milk and eggs together until fully combined. When the mixture is smooth, add the vanilla extract and 4 tablespoons of the melted butter. Stir this mixture well.
Pour half of the milk mixture over the flour mixture. Use a spatula to gently stir until a paste forms.
Once the paste is formed, gradually add the remaining milk mixture, stirring continuously until you create a very thin batter.
Cover the bowl with plastic wrap and refrigerate the batter for at least 30 minutes.
Heat a 10-inch nonstick skillet over medium heat. Brush the skillet lightly with a thin layer of the remaining melted butter.
Using a measuring cup, pour about 2 ounces of batter (approximately 1/4 cup) into the pan. Immediately swirl the pan to spread the batter evenly.
Cook the crepe until just set, about 30 seconds. Flip the crepe carefully using a spatula and cook for an additional few seconds until set.
For the filling, pulse the granulated sugar in a blender for about 30 seconds. Add the ricotta, lemon juice, and a pinch of salt, pulsing a few times to combine.
To assemble, take 2 to 3 tablespoons of the ricotta mixture and place it in the center of each crepe. Roll them up tightly.
