My best friend’s mom makes this for every Sunday supper, and the smell alone is incredible

For a slightly richer version, dot an extra tablespoon or two of butter over the top during the last 10 minutes of baking so it melts into the potatoes and onions. If you like a bit of color, you can use a mix of red and yellow potatoes, or swap in sweet onions for an even more caramelized flavor. To stretch the recipe for a bigger crowd, add up to 1 extra pound of potatoes and 1 more onion, then increase the butter and salt slightly and use a larger pan so everything can still roast, not steam. If you’re prepping ahead on a busy day, you can cut the potatoes and onions in the morning, toss them with melted butter and salt, cover, and refrigerate right in the pan; just give them a quick toss and roast as directed, adding 5–10 extra minutes if they’re going into the oven cold. For crisper edges, roast on a lower rack and don’t overcrowd the pan; for softer, more casserole-style potatoes, cover the pan loosely with foil for the first 20 minutes, then uncover to finish browning.