Preheat and prep: Heat your oven to 350°F (175°C). Grease a 12-cup muffin pan well with oil spray or brush with olive oil.
Whisk the base: In a large bowl, whisk eggs, heavy cream, garlic powder, onion powder, paprika, salt, and pepper until smooth and slightly frothy.
Add the mix-ins: Stir in cheese, spinach, bell pepper, green onions, and bacon or sausage if using.
Mix gently to distribute evenly.
Fill the cups: Divide the mixture among the 12 muffin cups, filling each about 3/4 full. Stir between pours to keep the solids evenly spread.
Bake: Place the pan on the middle rack and bake for 18–22 minutes, until the centers are set and the tops are lightly golden. A toothpick should come out mostly clean.
Cool slightly: Let the muffins rest in the pan for 5 minutes.
Run a thin knife around the edges to release, then transfer to a wire rack.
Serve or store: Enjoy warm, or let them cool fully before storing.