Herb Roasted Pork Tenderloin with Red Onion Jam

Bahan-bahan (4 porsi)

• 1 tablespoon salted butter
• 3 medium (about 1½ pounds) red onions, (thinly sliced)
• 2 teaspoons granulated white sugar
• 1 teaspoon salt, (divided)
• ¼ cup water
• 1 pound pork tenderloin
• ½ teaspoon coarse ground black pepper
• 1 tablespoon chopped fresh rosemary
• 1 medium garlic clove, (minced)
• 2 teaspoons olive oil