Preheat the oven to 400°F.
Place your cast-iron skillet in the oven while it heats — this helps everything caramelize instead of steam.
In a bowl, toss peppers and onions with olive oil, salt, pepper, and any herbs/spices you’re using.
Carefully remove the hot skillet.
Spread the veggies evenly in the pan. Nestle the sausages right on top.
Roast uncovered for 20 minutes.
Turn the sausages and stir the peppers/onions so they pick up the sausage drippings.
Return to oven for 15–20 more minutes, until sausages are deeply browned and cooked through and peppers and onions are soft with caramelized edges.
A tiny splash of balsamic or red wine vinegar right at the end wakes everything up beautifully.
