Make the Rhubarb Compote: In a small saucepan, combine rhubarb, sugar, lemon juice, and water. Cook over medium heat for 6–8 minutes until thickened. Cool completely.
Make the Dough: In a bowl, whisk flour, sugar, baking powder, baking soda, and salt. Cut in butter until crumbly. Mix in sourdough discard and milk until a soft dough forms. Chill for 15–20 minutes if needed.
Prepare the Filling: In a small bowl, mix cream cheese, strawberry jam, and vanilla until smooth.
Roll and Assemble: Preheat oven to 375°F (190°C). Roll dough into a 10x14-inch rectangle on a floured surface. Transfer to a parchment-lined baking sheet. Spread cream cheese filling down the center third, then top with cooled compote.
Braid: Cut 1-inch diagonal strips on both sides of the filling. Fold strips over, alternating sides, to form a braid. Tuck the ends.
Bake: Bake for 20–25 minutes or until golden brown. Cool for 10 minutes on the baking sheet.
Glaze (Optional): Mix powdered sugar with milk and vanilla or lemon juice. Drizzle over cooled braid.
Serve: Slice and enjoy warm or at room temperature.