Bring a large saucepan of water to a boil over high heat. Add the cauliflower and lemon wedge. Lower the heat and simmer until tender, about 10 minutes.Drain, blot dry, and transfer to a large bowl. Toss the lemon.
Stir in with the cauliflower, one tablespoon of the melted butter, 1 ½ tablespoon of the breadcrumbs, and the eggs, capers, garlic, oil, salt, and pepper. Transfer into a large, oval gratin baking dish.
In a small bowl, stir together the remaining breadcrumbs and remaining 1 tablespoon of butter, and sprinkle over the top.
Roast the cauliflower until golden brown on top, about 10 minutes. Sprinkle with parsley and serve warm.
Giangi's Kitchen provides nutritional information, but these figures should be considered estimates, as a registered dietician does not calculate them.