Combine rhubarb, sugar, and lemon juice in a saucepan, stir, and let stand 1 hour (off heat).
Add vanilla bean and scraped seeds to the saucepan and bring to a boil. Once boiling reduce heat to medium and simmer about 40 minutes until rhubarb is translucent and the mixture is a thick, syrupy mash. Stir often to prevent scorching.
Cool compote to room temperature before covering and refrigerating or freezing.