A caramelized onion recipe from MarthaStewart.com calls for melting 6 tablespoons of unsalted butter. Cut 15 medium yellow onions into 1/4-inch thick slices, and add them to the melted butter with 2 teaspoons of coarse salt. Cooking over medium heat, add 1 tablespoon of sugar, and cook for 35 to 40 minutes, stirring often and lowering the heat if any scorching occurs.
The finished product should be golden brown and have a consistency similar to that of jam. Remove the mixture from the heat, and let the caramelized onions cool. Add them to burgers, sandwiches, pizza or pastas.
BonAppetit.com recommends some adjustments to traditional caramelized onion recipes. The site advises cooks to use a combination of oil and butter instead of butter alone. The amount used determines the outcome. Less fat achieves the jam-like consistency, while more tends to fry the onions. Bon Appetit cautions against cooking the onions too quickly. Medium-low heat for 45 minutes is optimal.
Aim for soft onions, but not mushy ones. Deep color indicates the onions have caramelized. Do not ignore the bits on the bottom of the pan, but deglaze for added flavor. Use a pan large enough to accommodate your onions from the beginning. Too many onions in the pan causes steaming to occur, producing water and decreasing flavor.