Pile flour mixed with salt on a work surface, make a well in the center and add an egg to the well. Cut butter into small pieces and arrange around the well. Knead into a smooth pastry and wrap in foil, refrigerate for 30 minutes.
Peel rhubarb stalks. Cut into small pieces. Combine with lime juice, 100 grams (approximately 3 1/2 ounces) of honey and cinnamon. Cook for about 3 minutes and cool.
Roll out pastry into two circles. Line pan with one circle, making an edge all around. Spread with rhubarb mixture and top with another pastry circle. Press the edges together and prick pastry with a fork several times. If desired, decorate pie with remaining pastry. Brush with 3 tablespoons of milk. Bake in preheated oven at 200°C (approximately 400°F) for about 45 minutes.
Combine milk with vanilla extract and 30 grams (approximately 1 ounce) of honey, bring to a boil, stirring. Whisk cornstarch with 2 tablespoons of milk and egg yolks, add to milk and simmer until sauce thickens. Remove from heat and cool. Serve pie with chilled vanilla cream.