Broccoli and sharp cheddar baked into a thick frittata. This low carb Sunday breakfast feeds a crowd, tastes great at any temperature, and reheats perfectly.
Preheat the oven to 375°F. Place a 10-inch oven-safe skillet on the stovetop over medium heat.
Add the olive oil to the hot skillet. Sauté diced onion for 2–3 minutes until slightly softened, then add broccoli florets and cook for an additional 4 minutes, stirring occasionally, until broccoli is bright green.
In a large bowl, whisk together the eggs, milk, kosher salt, and black pepper until the mixture is fully blended and slightly frothy.
Spread the sautéed broccoli and onion evenly across the skillet. Pour the egg mixture over the vegetables, ensuring even distribution.
Top evenly with shredded cheddar cheese. Let cook on the stovetop for 2–3 minutes (without stirring) until the edges just begin to set, then transfer the skillet to the preheated oven.
Bake for 14–18 minutes, until the frittata is puffed, golden on top, and the center just barely jiggles. Rest for 5 minutes before slicing; serve warm, at room temperature, or chilled.