Filling:
Put 1/2 cup of sugar in a saucepan and add the water.
Put the saucepan over medium heat and bring to a boil, stirring to dissolve the sugar. Add the rhubarb, reduce heat to low, cover, and simmer until the rhubarb is tender (about 5 minutes).

Remove the saucepan from the heat and pass the rhubarb through a sieve.
Return the cooking liquid to the saucepan and bring to a boil.
Let boil for 2 minutes or until only 1/2 cup (125 ml) remains.
Set the reduced liquid aside.

Whip the ricotta with the remaining sugar, then add the lemon zest, cardamom, and rhubarb.

Preheat the oven to 400 F (200 C).

Butter a baking dish.

Place 1/8 of the ricotta and rhubarb mixture in the center of each cooked crepe.
Fold the sides and roll the crepe to form a small bundle.
Place the crepes in the baking dish, folded side down, and cover with aluminum foil.

Bake for 15 to 20 minutes or until the filling is hot.
Reheat the cooking liquid in a small saucepan.
Drizzle the crepes with rhubarb sauce and serve.

Crepes:
In a large bowl, sift the flour and salt.
Make a well in the center and add the eggs.
Beat the eggs into the flour and gradually add the milk.
Whip until a smooth mixture forms and add the melted butter.
Cover and refrigerate for 1 hour.

Remove the mixture from the refrigerator and stir to check the consistency (it should resemble liquid cream). Add milk if necessary.
The crepe batter is ready to use.