Preheat your oven to 400°F and lightly oil a large oven-safe skillet (or Dutch oven).
Dice the zucchini, yellow squash, and calabacita squash. Heat olive oil over medium-high heat and sauté for about 8-10 minutes, stirring occasionally, until softened.
Dice the shallots and stir them into the skillet. Cook for an additional 2-3 minutes, allowing them to sweat and become fragrant.
Add the cauliflower rice, black beans, sweet corn, garlic powder, salt, and pepper. Stir everything together until evenly combined.
Mix in half of the shredded cheddar cheese, ensuring it melts into the mixture.
Pat the mixture down evenly into the skillet, then sprinkle the remaining cheddar cheese on top.
Transfer the skillet to the oven and bake for 10 minutes, or until the cheese is bubbly and golden-brown.
Remove the skillet from the oven and let it cool for 5-10 minutes. Sprinkle with fresh parsley for brightness.
Serve warm and top with a dollop of sour cream if desired. Enjoy!