New York Style Onion Sauce

Pro tips

• Slice onions thinly and evenly so they caramelize uniformly without burning. Use a mandoline for consistency.
• Cook over medium heat and stir frequently to prevent sticking and ensure the onions turn golden brown, not dark brown.
• Add the ketchup and mustard toward the end to preserve their tangy flavor and prevent them from scorching.
• Taste and adjust sweetness or tanginess by adding more brown sugar, ketchup, or mustard to match your preference.

Substitutions

• White or yellow onions → Spanish onions (milder sweetness, acceptable swap)
• Brown sugar → white sugar or honey (white sugar is less rich; honey adds depth)
• Butter → neutral oil (works but loses richness)
• Ketchup → tomato paste diluted with water (more concentrated, use less)

Storage & make-ahead

Store in an airtight container in the refrigerator for up to 5 days. Reheat gently on the stovetop or microwave before serving.

How long does it take to make New York style onion sauce?

About 15–20 minutes on the stovetop, including slicing and caramelizing the onions.

Can I make this sauce ahead of time?

Yes. Prepare up to 2 days ahead, store in an airtight container in the refrigerator, and reheat gently on the stovetop or microwave before serving.

What's the best way to slice onions for this sauce?

Use a sharp knife or mandoline to slice Spanish onions into thin, even slices so they caramelize uniformly.

Can I use white onions instead of Spanish onions?

Yes, white or yellow onions work well and will caramelize similarly, though Spanish onions have a slightly sweeter flavor.

How should I store leftover onion sauce?

Transfer to a clean jar or airtight container and refrigerate for up to 5 days. Reheat on the stovetop over low heat, stirring occasionally.