Buttermilk Panna Cotta with Rhubarb Strawberry Jelly

INGREDIENTS

• 1 1/4 unflavored powdered gelatin
• 1 1/4 heavy cream
• 1/3 sugar
• 1/4 kosher salt
• 1/4 vanilla bean, halved lengthwise
• 1 1/4 buttermilk
• 1 crème fraîche or sour cream
• 6 strawberries, hulled (about 1 cup)
• 1/4 sugar
• 12 rhubarb, trimmed, sliced 1/4-inch thick (about 3 cups), divided
• 1/2 unflavored powdered gelatin