Preparation

• Prepare a medium (350°F to 375°F) gas or charcoal grill fire. Brush the onion slices  with oil and season with salt and pepper.
• Grill the onion slices until grill marks form on one side, about 7 to 8 minutes. Flip the slices and continue to grill until tender, about 7 to 8 minutes more. Stack the onions on a large piece of foil, wrap the onions up, and let them sit for 10 minutes to soften further.
• Pulse the onions in a food processor until coarsely chopped. Add the yogurt, mayonnaise, Gorgonzola, lemon juice, garlic, hot sauce, 1/2 tsp. salt, and 1/4 tsp. pepper; pulse until combined but still chunky.
• Transfer to a serving bowl, cover, and chill for at least 1 hour. Garnish with chives before serving.

Make Ahead Tips

The dip can be made and refrigerated up to 1 week ahead. Return to cool room temperature to serve.