Cooking spray or oil
1 pound broccoli (about 1 medium head)
1 pint cherry tomatoes halved
12 large eggs
1 cup whole milk
1 teaspoon kosher salt
1/2 teaspoon freshly ground black pepper
1 cup shredded sharp cheddar cheese
Arrange a rack in the middle of the oven and heat to 375°F. Generously coat a rimmed baking sheet with cooking spray or oil.
Cut the broccoli florets from the stalks. Peel the stalks with a vegetable peeler, then chop the stalks and florets into bite-size pieces. Arrange the broccoli and tomatoes on the baking sheet in a single layer.
Roast until the broccoli is tender, 12 to 15 minutes. Meanwhile, whisk the eggs, milk, salt, and pepper together in a large bowl or spouted measuring cup.
Carefully pour the eggs onto the baking sheet over the vegetables. Sprinkle with the cheese. Bake until the frittata is puffed around the edges, golden in spots, and a knife inserted in the center comes out clean, 25 to 30 minutes. Cool completely before slicing.