Broccoli Cheese Casserole (Creamy, Cheesy, Golden)

Ingredients

• Cooking spray or 1 teaspoon butter, for the baking dish
• 1 1/2 lb (680 g) broccoli crowns, cut into bite-size florets
• 1 can (10.5 oz / 298 g) condensed cream of mushroom soup
• 3/4 cup (170 g) mayonnaise
• 2 large eggs
• 1/2 small yellow onion, finely grated or minced
• 2 cups (225 g) freshly shredded sharp cheddar cheese, divided
• 1/2 teaspoon kosher salt
• 1/4 teaspoon black pepper
• 1/4 teaspoon garlic powder
• 1 sleeve buttery round crackers, about 35 crackers, roughly crushed
• 3 tablespoons (42 g) unsalted butter, melted