Tenderloin Steaks with Red Onion Marmalade

Ingredients:

• Cooking spray
• 1 large red onion, sliced and separated into rings (about 2 cups)
• 2 tablespoons red wine vinegar
• 2 tablespoons honey
• 1/2 teaspoon salt, divided
• 1 teaspoon dried thyme
• 1/4 teaspoon freshly ground black pepper
• 4 (4-ounce) beef tenderloin steaks, trimmed (1 inch thick)

Source