Preheat your oven to 375°F (190°C).

Chop the cauliflower, zucchini, bell peppers, and onion into small, even pieces.

Heat olive oil in a large skillet over medium heat. Add minced garlic and diced onion, sautéing until fragrant.

Add the chopped cauliflower, zucchini, and bell peppers to the skillet. Sauté until tender.

Stir in the cream or vegetable broth, add spices and cheddar cheese, and mix well.

Grease a baking dish, transfer the mixture, and spread it evenly.

Bake the casserole in the preheated oven for 25 to 30 minutes.

Remove from oven and let it rest for 5 to 10 minutes before serving.