• 1 stick unsalted butter , cut into pieces
• 1 1/2 tsp. kosher salt
• 3 large yellow onions , thinly sliced
• 1 bay leaf
• 3 whole black peppercorns
• 1 strip lemon zest

In a large saucepan, bring 1/3 cup water to a boil. Whisk in butter and salt until melted. Reduce heat to low and add remaining ingredients; toss gently to coat.

Make a lid by cutting a piece of parchment paper the same size as the top of the pan, and place directly on onions. Cook about 2 hours, turning every 20 minutes, until onions have no color and are soft but not falling apart. If all liquid evaporates, add 1/4 cup water. Remove from heat and let cool in liquid. Discard bay leaf, peppercorns, and zest. Transfer onions to an airtight container; they can be kept refrigerated for up to 1 week.

Note: The onions can be used with other recipes and served in any number of ways. This is one of our favorites: Toast a baguette, spread apricot jam on top, add a heap of onions, and top with slices of prosciutto.