Preheat oven to 375. Butter a large baking dish. Place rhubarb in baking dish. Spread out and add lemon juice. Sprinkle vanilla sugar & brown sugar over rhubarb. Dot with butter. Bake 15 minutes. Pour cream around rhubarb & return to oven for 5 minutes. Approximately 12-20 minutes. Note: to make vanilla sugar, place a vanilla bean in a jar, cover with granulated sugar, close with a tight lid. Store for 1 week and you have wonderful vanilla sugar for all your favorite desserts!