Step 1

Preheat the oven to 400°F

Step 2

Heat the oil in a large oven-safe cast-iron skillet over medium heat

Step 3

Add the vegetables and squash and sear, stirring occasionally, until well browned

Step 4

Transfer to a bowl, reserving the skillet

Step 5

Place the skillet over medium-high heat, add the onion and Brussels sprouts and sear, stirring occasionally

Step 6

(Add a little more oil, if necessary

Step 7

) When the onion softens and the sprouts start to brown on the edges, add the reserved seared vegetables and the sliced apple to the skillet

Step 8

Toss or stir the ingredients, then add salt and pepper to taste

Step 9

Transfer the pan to the oven and roast until the vegetables are cooked through, 5 to 15 minutes

Step 10

Check the seasonings and serve