Grilled Pork Tenderloin with Rhubarb Barbecue Sauce

Ingredients

• 2 tablespoons olive oil, divided
• 1/2 cup finely chopped onion
• 1 clove garlic, chopped
• 2 cups chopped rhubarb (about 8 ounces), fresh or frozen
• 1/4 cup water
• 2 tablespoons tomato paste
• 5 tablespoons light brown sugar
• 1 tablespoon apple cider vinegar
• 1 teaspoon Worcestershire sauce
• 1 teaspoon Dijon mustard
• 1/4 teaspoon chipotle powder
• 1/2 teaspoon paprika
• 1 teaspoon salt, divided
• 1 pound pork tenderloin
• 1/2 teaspoon pepper