Preheat the oven to 375 degrees F (190 degrees C). Grease a 9x13-inch baking dish.

Beat together eggs, cottage cheese, and melted butter in a large bowl until well combined. Stir in cornbread mix until just moistened. Fold in broccoli, onion, and 1 cup Cheddar cheese. Pour into the prepared baking dish and sprinkle with remaining 1/2 cup Cheddar cheese.

Bake in the preheated oven until a toothpick inserted into the center comes out clean, 35 to 40 minutes. Cool in the baking dish for 10 minutes before slicing and serving warm.