very good and can be made ahead
2 large Vidalia onions, cut crosswise into 1⁄2″-thick slices
4 tbsp. extra-virgin olive oil
Kosher salt and freshly ground black pepper, to taste
6 tbsp. bread crumbs
2 tbsp. unsalted butter, melted
1 tbsp. finely chopped parsley
1 tsp. finely chopped oregano
1 tsp. finely chopped thyme
2 cloves garlic, minced
Heat oven to 450°. On a foil-lined baking sheet, coat onion slices in oil, keeping them as intact as possible; season with salt and pepper. Bake, turning once, until soft and lightly caramelized, about 15 minutes.
Meanwhile, stir together bread crumbs, butter, parsley, oregano, thyme, garlic, and salt and pepper in a small bowl; sprinkle evenly over onion slices. [ at this point you can refrigerate until ready to use – up to two days ahead] Continue baking until topping is golden brown, about 15 minutes more.