Cut each onion in half, then place onions cut side down and slice off each end.
Peel off papery skin, then cut onions in ¾-inch-thick wedges.
Put onion wedges in a large bowl, and add olive oil, salt and pepper.
Toss until wedges separate a bit and are evenly coated in oil.
Line a sheet pan with parchment paper or nonstick foil.
Distribute onions on the sheet pan in a single layer.
Roast for 15 minutes, then stir.
Roast for an additional 10-15 minutes, depending on how caramelized you want the edges of your onions to be.
Notes
Storage Tips: Store in an airtight container in the refrigerator for up to 4 days.Expert Tips: Add herbs like rosemary or thyme to the onions, or season them with spices like chili powder, garlic salt, curry powder, or smoked paprika. You can also add a splash or two of balsamic vinegar to your sliced red onions to make balsamic roasted onions. Don’t crowd the onions onto a small baking sheet—they need to be distributed in a single layer so that they caramelize rather than steam. Using nonstick foil or parchment paper on your baking sheet makes cleanup easy. Plus, the onions won’t stick to your pan.